Summary
Clinical characteristics.
Von Hippel-Lindau (VHL) syndrome is characterized by hemangioblastomas of the brain, spinal cord, and retina; renal cysts and clear cell renal cell carcinoma; pheochromocytoma, pancreatic cysts, and neuroendocrine tumors; endolymphatic sac tumors; and epididymal and broad ligament cysts. Cerebellar hemangioblastomas may be associated with headache, vomiting, gait disturbances, or ataxia. Spinal hemangioblastomas and related syrinx usually present with pain. Sensory and motor loss may develop with cord compression. Retinal hemangioblastomas may be the initial manifestation of VHL syndrome and can cause vision loss. Renal cell carcinoma occurs in about 70% of individuals with VHL and is the leading cause of mortality. Pheochromocytomas can be asymptomatic but may cause sustained or episodic hypertension. Pancreatic lesions often remain asymptomatic and rarely cause endocrine or exocrine insufficiency. Endolymphatic sac tumors can cause hearing loss of varying severity, which can be a presenting symptom. Cystadenomas of the epididymis are relatively common. They rarely cause problems, unless bilateral, in which case they may result in infertility.
Management.
Treatment of manifestations: Intervention for most CNS lesions (remove brain and spinal lesions completely when large and/or symptomatic); treat retinal (but not optic nerve) angiomas prospectively; early surgery (nephron-sparing or partial nephrectomy when possible) for renal cell carcinoma; renal transplantation following bilateral nephrectomy; remove pheochromocytomas (partial adrenalectomy when possible); monitor pancreatic cysts and neuroendocrine tumors and consider removal of neuroendocrine tumors; consider surgical removal of endolymphatic sac tumors (particularly small tumors in order to preserve hearing and vestibular function); cystadenomas of the epididymis or broad ligament need treatment when symptomatic or threatening fertility.
Prevention of secondary complications: Early detection and removal of tumors to prevent/minimize secondary deficits such as hearing loss, vision loss, neurologic symptoms, and the need for renal replacement therapy.
Surveillance: For individuals with VHL syndrome, those with a VHL pathogenic variant, and at-risk relatives of unknown genetic status:
Starting at age one year: Annual evaluation for neurologic symptoms, vision problems, and hearing disturbance; annual blood pressure monitoring; annual ophthalmology evaluation.
Starting at age five years: Annual plasma or 24-hour urine for fractionated metanephrines; audiology assessment every two to three years; thin-slice MRI with contrast of the internal auditory canal in those with repeat ear infections.
Starting at age 16 years: Annual abdominal ultrasound; MRI scan of the abdomen and MRI of the brain and total spine every two years.
Agents/circumstances to avoid: Tobacco products should be avoided since they are considered a risk factor for kidney cancer; chemicals and industrial toxins known to affect VHL-involved organs should be avoided; contact sports should be avoided if adrenal or pancreatic lesions are present.
Evaluation of relatives at risk: If the pathogenic variant in a family is known, molecular genetic testing can be used to clarify the genetic status of at-risk family members to eliminate the need for surveillance of family members who have not inherited the pathogenic variant.
Pregnancy management: Intensified surveillance for cerebellar hemangioblastoma and pheochromocytoma during preconception and pregnancy; MRI without contrast of the cerebellum at four months' gestation.
Genetic counseling.
VHL syndrome is inherited in an autosomal dominant manner. Approximately 80% of individuals with VHL syndrome have an affected parent and about 20% have VHL syndrome as the result of a de novo pathogenic variant. Parental mosaicism has been described; the incidence is not known. The offspring of an individual with VHL syndrome are at a 50% risk of inheriting the VHL pathogenic variant. Prenatal testing for a pregnancy at risk is possible if the pathogenic variant has been identified in a family member.
Diagnosis
No formal diagnostic criteria have been published.
Suggestive Findings
Von Hippel-Lindau syndrome should be suspected in individuals with or without a family history of VHL who have:
Retinal angioma, especially in a young individual
Spinal or cerebellar hemangioblastoma
Adrenal or extra-adrenal pheochromocytoma
Renal cell carcinoma, if the individual is younger than age 47 years or has a personal or family history of any other tumor typical of VHL
Multiple renal and pancreatic cysts
Neuroendocrine tumors of the pancreas
Endolymphatic sac tumors
Less commonly, multiple papillary cystadenomas of the epididymis or broad ligament
Establishing the Diagnosis
The diagnosis of von Hippel-Lindau (VHL) syndrome is established in a proband with the clinical features listed below [Lonser et al 2003, Butman et al 2008, Maher et al 2011] and/or by identification of a heterozygous germline pathogenic variant in VHL on molecular genetic testing. Identification of a heterozygous germline pathogenic variant in VHL by molecular genetic testing (Table 1) establishes the diagnosis and supports periodic follow up even if clinical and radiographic features are inconclusive.
Various tests can be used to establish the diagnosis and determine the extent of the clinical manifestations (MRI of the brain and spinal cord, fundoscopy, ultrasound examination / MRI of the abdomen, and blood/urinary catecholamine metabolites can be used to establish the clinical diagnosis). See Surveillance.
Clinical diagnostic criteria
Note: Other lesions characteristic of VHL are endolymphatic sac tumors (ELST) and pancreatic neuroendocrine tumors; however, these are not typically used to make a clinical diagnosis of VHL. ELST presents as a mass on the posterior wall of the petrous part of the temporal bone and can be missed on standard MRI. MRI with contrast and high signal intensity with T1 using thin slices of the internal auditory canal is recommended in symptomatic individuals.
Molecular genetic testing. Approaches can include a combination of gene-targeted testing (single-gene testing, multigene panel) and comprehensive
genomic testing (exome sequencing, genome sequencing, exome array) depending on the phenotype.
Gene-targeted testing requires that the clinician determine which gene(s) are likely involved, whereas genomic testing does not. Because the phenotype of VHL is broad, individuals with the distinctive features described in Suggestive Findings are likely to be diagnosed using gene-targeted testing (see Option 1), whereas those with a phenotype indistinguishable from many other inherited disorders associated with an increased risk of tumors are more likely to be diagnosed using genomic testing (see Option 2).
Option 1
When the phenotypic, laboratory, and radiographic findings suggest the diagnosis of VHL molecular genetic testing approaches can include single-gene testing or use of a multigene panel.
Single-gene testing. Sequence analysis of the VHL coding region, intron 1, and flanking sequences will identify small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. If no pathogenic variant is found perform gene-targeted deletion/duplication analysis to detect intragenic deletions or duplications.
A multigene panel that includes VHL and other genes of interest (see Differential Diagnosis) is most likely to identify the genetic cause of the condition while limiting identification of variants of uncertain significance and pathogenic variants in genes that do not explain the underlying phenotype. Note: (1) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (2) Some multigene panels may include genes not associated with the condition discussed in this GeneReview. (3) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician. (4) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests. For this disorder a multigene panel that also includes deletion/duplication analysis is recommended (see Table 1).
For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.
Option 2
When the phenotype is indistinguishable from many other inherited disorders characterized by tumors, comprehensive
genomic testing (which does not require the clinician to determine which gene[s] are likely involved) is the best option. Exome sequencing is most commonly used; genome sequencing is also possible. Exome array (when clinically available) may be considered if exome sequencing is not diagnostic.
For an introduction to comprehensive genomic testing click here. More detailed information for clinicians ordering genomic testing can be found here.
Table 1.
Molecular Genetic Testing Used in von Hippel-Lindau Syndrome
View in own window
Gene 1 | Method | Proportion of Probands with a Pathogenic Variant 2 Detectable by Method |
---|
VHL
| Sequence analysis 3, 4 | ~89% 5 |
Gene-targeted deletion/duplication analysis 6 | ~11% 5 |
- 1.
- 2.
- 3.
- 4.
- 5.
- 6.
Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include a range of techniques such as quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications.
Clinical Characteristics
Clinical Description
Von Hippel-Lindau (VHL) syndrome is characterized by hemangioblastomas of the brain, spinal cord, and retina; renal cysts and renal cell carcinoma; pheochromocytoma and paraganglioma; pancreatic cysts and neuroendocrine tumors; endolymphatic sac tumors; and epididymal and broad ligament cysts. Some clustering of tumors occurs, resulting in the designation of specific VHL syndrome phenotypes. The manifestations and severity are highly variable both within and between families, even among those with the same pathogenic variant. One study showed that in adulthood, men have more VHL manifestations compared to women. They also showed that the risk for manifestations was not constant, but varied throughout the affected individual's lifetime [Binderup et al 2016]. Age was the only predictor for the number of involved organs. The sex of the affected individual or type/location of the VHL pathogenic variant were not associated with the number of involved organs [Feletti et al 2016].
Hemangioblastomas. CNS hemangioblastoma is the prototypic lesion of VHL syndrome [Catapano et al 2005, Gläsker 2005]. Multiple CNS tumors, occurring either synchronously or metachronously, are common. Roughly 80% develop in the brain and 20% in the spinal cord. Peripheral nerve hemangiomas may be a rare manifestation [Giannini et al 1998].
Hemangioblastomas oscillate between periods of growth and stability [Wanebo et al 2003] and are generally slow growing, but on occasion include rapidly enlarging cysts that produce hydrocephaly with papilledema. Some hemangioblastomas do not cause symptoms and are discovered only on imaging.
Central nervous system (CNS) hemangioblastoma growth appears to be associated with male sex and partial germline deletions [Lonser et al 2014, Huntoon et al 2015]. Growth patterns of these lesions can be saltatory (72%), linear (6%), or exponential (22%). Increased growth was associated with male sex, symptomatic tumors, and hemangioblastoma-associated cysts. CNS hemangioblastomas remain the main cause of death, although VHL-related survival has improved over the years [Binderup et al 2017b].
Brain hemangioblastomas. Within the brain, the vast majority are infratentorial, mainly in the cerebellar hemispheres. The pituitary stalk is the most common site for the development of supratentorial hemangioblastomas in individuals with VHL syndrome [
Lonser et al 2009]. Clinical symptoms depend on the site of the tumor: with infratentorial tumors, headache, vomiting, and gait disturbances or ataxia predominate; with tumors above the tentorium, symptoms depend on the location of the lesion.
Spinal hemangioblastomas are generally intradural, most commonly occur in the cervical or thoracic regions, and occasionally may involve the entire cord. Most symptom-producing spinal hemangioblastomas are associated with cysts/syringomyelia/syrinx [
Wanebo et al 2003]. Spinal hemangioblastomas usually present with pain; sensory and motor loss may develop with cord compression.
Retinal hemangioblastoma. These retinal lesions, sometimes called retinal angiomas, are histologically identical to CNS hemangioblastomas. They may be the initial manifestations of VHL syndrome and may occur in childhood. About 70% of affected individuals are identified as having retinal angiomas [
Webster et al 1999,
Kreusel 2005] with mean age of detection about 25 years [
Dollfus et al 2002]. The tumors are most often located in the temporal periphery of the retina with feeder and draining vessels going to and from the optic disc. However, they may develop in the posterior pole (1%) and optic disc (8%).
Retinal hemangioblastomas may be asymptomatic and may be detected on routine ophthalmoscopy. Others present with a visual field defect or a loss of visual activity resulting from retinal detachment, exudation, or hemorrhage. Tests of retinal function may be abnormal even in the presence of quiescent retinal angiomas [
Kreusel et al 2006]. While the number of retinal angiomas does not appear to increase with age, the probability of vision loss does [
Kreusel et al 2006].
Renal lesions
Multiple and bilateral renal cysts are common in individuals with VHL syndrome [
Lonser et al 2003].
Renal cell carcinoma (RCC), specifically of the clear cell subtype, developing either within a cyst or in the surrounding parenchyma, occurs in about 70% of affected individuals by age 60 years, and is a leading cause of mortality in VHL syndrome [
Maher et al 1990,
Maher et al 1991]. Pathogenic variants in
VHL are the most common cause of
familial and
sporadic RCC. Overall survival for renal cell carcinoma in individuals with VHL is associated with tumor size (<3 cm or ≥3 cm) and age of the individual [
Kwon et al 2014].
Pheochromocytoma may cause sustained or episodic hypertension or may not cause signs/symptoms and is detected incidentally by an abdominal imaging procedure. Pheochromocytomas are usually located in one or both adrenal glands. They are usually benign, but malignant behavior has been reported [Chen et al 2001, Jimenez et al 2009].
Paragangliomas. Similar in etiology, paragangliomas can develop along the sympathetic axis in the abdomen or thorax [Schimke et al 1998, Boedeker et al 2014]; these tumors are often nonfunctional (i.e., do not secrete catecholamines or other hormones).
Pancreatic lesions
Pancreatic cysts. Most pancreatic lesions are simple cysts and have no malignant potential. While they can be numerous in individuals with VHL, they rarely cause endocrine or exocrine insufficiency. Occasionally, cysts in the head of the pancreas cause biliary obstruction.
Endolymphatic sac tumors are seen in approximately 10%-16% of individuals with VHL syndrome, and in some instances the associated uni- or bilateral hearing loss is the initial feature of the syndrome [Kim et al 2005, Binderup et al 2013b]. The onset of hearing loss is typically sudden; severity varies, but it is often severe to profound [Choo et al 2004, Kim et al 2005]. Vertigo or tinnitus is the presenting complaint. More significant hearing loss and larger tumor size at presentation was reported in individuals with endolymphatic sac tumors not related to VHL than in individuals with VHL-related endolymphatic sac tumors [Nevoux et al 2014]. Large endolymphatic sac tumors can involve other cranial nerves. Endolymphatic sac tumors are rarely malignant [Muzumdar et al 2006].
Epididymal and broad ligament cystadenomas. Epididymal or papillary cystadenomas are relatively common in males with VHL syndrome. They rarely cause problems, unless bilateral, in which case they may result in infertility. The equivalent, much less common, lesion in women is a papillary cystadenoma of the broad ligament. Both tissues are mesonephric in origin and are likely a developmental remnant of somatic VHL loss.
Genotype-Phenotype Correlations
Four general VHL syndrome phenotypes (type 1, type 2A, type 2B, type 2C) have been suggested based on the likelihood of pheochromocytoma or renal cell carcinoma. Many lines of research support the conclusion that the molecular etiology of pheochromocytomas appears to be distinct from other VHL lesions. Therefore, the most relevant genotype-phenotype correlations rely mostly on scoring the presence/absence of pheochromocytomas associated with a given allele. The following discussion summarizes the genotype-phenotype studies published to date, with the cautionary note that further investigation is needed. Note: Patterns are not clear-cut, and genotype-phenotype correlations have no current diagnostic or therapeutic value and are used for academic purposes only.
VHL type 1. Retinal angioma, CNS hemangioblastoma, renal cell carcinoma, pancreatic cysts, and neuroendocrine tumors. VHL type 1 is characterized by a low risk for pheochromocytoma. Pathogenic truncating or missense variants that are predicted to grossly disrupt the folding of the VHL protein [Stebbins et al 1999] are associated with VHL type 1.
VHL type 2. Pheochromocytoma, retinal angiomas, and CNS hemangioblastoma. VHL type 2 is characterized by a high risk for pheochromocytoma. Individuals with VHL type 2 commonly have a pathogenic missense variant. Some pathogenic missense variants appear to correlate with a specific type 2 VHL phenotype [Weirich et al 2002, Sansó et al 2004, Abbott et al 2006, Knauth et al 2006] (see also Molecular Genetics). Pathogenic missense variants stratified by multiple in silico computational models found that variants with a high predicted risk of pathogenicity were predictive of pancreatic lesion progression in an NIH patient series [Tirosh et al 2018]. In contrast, genotype did not appear to influence the growth of renal cell carcinomas in individuals with VHL [Farhadi et al 2018].
VHL type 2 is further subdivided:
Type 2A. Pheochromocytoma, retinal angiomas, and CNS hemangioblastoma; low risk for renal cell carcinoma
Type 2B. Pheochromocytoma, retinal angiomas, CNS hemangioblastoma, pancreatic cysts, and neuroendocrine tumors; high risk for renal carcinoma
Type 2C. Risk for pheochromocytomas only
Several groups report a reduced risk for renal cell carcinoma in individuals with a deletion of VHL [Cybulski et al 2002, Maranchie et al 2004, McNeill et al 2009]. In particular, individuals with a complete or partial deletion that extends 5' of VHL to include BRK1 (previously C3orf10) have a significantly reduced risk of renal cell carcinoma [Maranchie et al 2004, McNeill et al 2009]. This genotype may constitute a distinct phenotype, VHL type 1B, characterized by a reduced risk for both renal cell carcinoma and pheochromocytoma.
Some individuals within families with apparent type 2C syndrome have developed hemangioblastomas [Neumann & Eng 2009].
Nomenclature
Obsolete terms for VHL syndrome include: angiophakomatosis retinae et cerebelli, familial cerebello-retinal angiomatosis, cerebelloretinal hemangioblastomatosis, Hippel disease, Hippel-Lindau syndrome, Lindau disease, and retinocerebellar angiomatosis [Molino et al 2006].
Prevalence
The incidence of VHL syndrome is thought to be about one in 36,000 births with an estimated de novo mutation rate of 4.4x10-6 gametes per generation [Maher et al 1991].
Differential Diagnosis
Isolated hemangioblastoma, retinal angioma, or clear cell renal cell carcinoma. The clinical sensitivity of molecular genetic testing of VHL makes it possible to effectively rule out von Hippel-Lindau (VHL) syndrome with a high degree of certainty in individuals with (1) isolated hemangioblastoma, retinal angioma, or clear cell renal cell carcinoma and (2) no detectable germline VHL pathogenic variant. Somatic mosaicism for a VHL pathogenic variant could still be considered in such individuals. A younger individual, especially one with multiple lesions, is more likely to have a germline VHL pathogenic variant than an older individual with a single lesion [Binderup et al 2017a].
Pheochromocytoma. Approximately 25% of individuals with pheochromocytoma and no known family history of pheochromocytoma have a heterozygous pathogenic variant in one of several genes: MAX, RET, SDHA, SDHAF2, SDHB, SDHC, SDHD, TMEM127, or VHL. Germline VHL pathogenic variants are rare in simplex cases of unilateral pheochromocytoma (i.e., an affected individual with no family history of VHL syndrome), unless the individual is younger than age 20 years.
Multiple endocrine neoplasia type 2
(MEN2). Individuals with MEN2A are at increased risk for medullary carcinoma of the thyroid, pheochromocytoma, and parathyroid adenoma or hyperplasia. Pheochromocytomas usually present after medullary thyroid cancer (MTC) or concomitantly; however, they are the first sign in 13%-27% of individuals with MEN2A [
Inabnet et al 2000,
Rodriguez et al 2008]. Features of MEN2B include mucosal neuromas of the lips and tongue, distinctive facies with thick vermilion of the upper and lower lips, ganglioneuromatosis of the gastrointestinal tract, a "marfanoid" habitus, and an increased risk for MTC and pheochromocytoma. Pheochromocytomas occur in 50% of individuals with MEN2B; about half are multiple and often bilateral. A
heterozygous pathogenic variant of
RET is associated with MEN2.
Hereditary paraganglioma-pheochromocytoma syndrome. Approximately 8.5% of individuals with apparently nonfamilial nonsyndromic pheochromocytoma have been shown to have a
pathogenic variant in one of the genes (
SDHD,
SDHB,
SDHA,
SDHC, and
SDHAF2) encoding the succinate dehydrogenase subunits that cause the hereditary paraganglioma-pheochromocytoma syndromes. Pathogenic variants in these genes are associated with
familial paragangliomas, which are also known as extra-adrenal pheochromocytomas or glomus tumors.
Korpershoek et al [2011] found an
SDHA germline pathogenic variant in 3% of individuals with apparently
sporadic paragangliomas and pheochromocytomas. A
heterozygous germline
TMEM127 or
MAX pathogenic variant has also been reported in a small percentage of individuals with hereditary paraganglioma-pheochormocytoma syndrome.
Renal cell carcinoma (RCC). Individuals with familial RCC should be examined for hereditary leiomyomatosis and renal cell cancer (HLRCC) and Birt-Hogg-Dubé (BHD) syndrome.
Endolymphatic sac tumors in VHL are often misdiagnosed as Menière disease.
Management
Evaluations Following Initial Diagnosis
To establish the extent of disease and needs in an individual diagnosed with von Hippel-Lindau (VHL) syndrome, the evaluations summarized in Table 2 (if not performed as part of the evaluation that led to the diagnosis) are recommended.
Table 2.
Recommended Evaluations Following Initial Diagnosis in Individuals with von Hippel-Lindau Syndrome
View in own window
System/Concern
|
Evaluation
|
Comment
|
Eyes
| Ophthalmologic evaluation | Check for retinal hemangioblastomas. |
Neurologic
| Neurologic history & physical exam |
|
ENT/Mouth
| Audiologic evaluation | Check for hearing loss associated w/endolymphatic sac tumors. |
Renal
| Abdominal ultrasound examination after age 16 yrs | Evaluate suspicious lesions in kidney, adrenal gland, or pancreas by more sophisticated techniques (e.g., CT, MRI). |
Endocrine
|
| To evaluate for pheochromocytoma |
Miscellaneous/
Other
| Consultation w/clinical geneticist &/or genetic counselor | |
Treatment of Manifestations
No guidelines exist for the management of VHL lesions.
CNS hemangioblastoma
Most central nervous system (CNS) hemangioblastomas can be surgically removed completely and safely [
Gläsker et al 2013].
Some advocate early surgical removal of both symptomatic and asymptomatic CNS lesions, while others follow asymptomatic lesions with yearly imaging studies. A recent study of 15 symptomatic individuals with
cauda equina hemangioblastomas revealed a worse outcome in only one individual six months after surgery. The other individuals were stable or improved [
Mehta et al 2017]. A retrospective study with a mean follow-up time of 21 months confirmed that microsurgical treatment of symptomatic spinal cord hemangioblastomas was safe and effective. Intraoperative fluorescence angiography was helpful in reducing intraoperative bleeding and preventing spinal swelling.
Surgical intervention of cysts/syrinx in the spinal cord is recommended.
Preoperative arterial embolization may be indicated, especially for extensive spinal tumors.
Pathologic findings during intraoperative neurophysiologic monitoring appear to predict worse long-term outcome after microsurgical removal of spinal cord hemangioblastomas [
Siller et al 2017].
Stereotactic therapy is increasingly popular, but there is still a need for prospective studies [
Pan et al 2018]. Gamma knife surgery may be useful with small solid tumors or those in inoperable sites [
Asthagiri et al 2010,
Simone et al 2011]. While this technique may reduce the size of the solid tumor, it does not appear to prevent cyst formation. The unpredictable growth pattern makes it difficult to determine when to start stereotactic therapy in order to avoid unnecessary intervention. A recent study with a mean follow up of 54 months in 19 individuals with 34 tumors revealed that 94% of tumors were radiographically stable or showed signs of regression. Local control rates at one, three, and five years were 96%, 92%, and 92%, respectively. Clinically 13 of 16 (81.2%) tumors had symptomatic improvement [
Pan et al 2017].
Similar results were demonstrated for local tumor control after stereotactic therapy: 93% after three years, 89% after five years, and 79% after ten years [
Kano et al 2015]. Factors associated with tumor control are solid, smaller, VHL-associated lesions and higher margin dose. Thirteen of the 186 (7%) experienced complications, 11 individuals needed steroid therapy and one person died of refractory peritumoral edema. Two individuals required additional surgery.
Another study showed a recurrence-free survival in six of eight individuals at a mean follow up of 48 months. Two individuals required additional surgery for persisting cerebellar symptoms. One individual showed an increase in cyst volume along with a decrease of the size of the mural nodule [
Goyal et al 2016].
A case study showed complete loss of stromal cells after a standard dose of SRS for hemangioblastoma, indicating the effectiveness of the treatment [
Nambu et al 2018].
Retinal hemangioblastoma
Most ophthalmologists favor prospective treatment of retinal (but not optic nerve) angiomas to avoid blindness, although spontaneous regression has occurred.
Ultra-widefield fluorescein angiography can be useful in the evaluation and management of retinal hemangioblatoma. This technique appears to detect more hemangioblastomas than ophthalmoscopy and conventional angiography [
Chen et al 2018].
Therapeutic modalities used to treat retinal hemangioblastomas include diathermy, xenon, laser, and cryocoagulation, with variable degrees of success depending on the location, size, and number of lesions. Recurrent tumors have been noted, even after many years, but some may be new tumors in the same general area rather than recurrent disease.
There is no evidence to support the use of sunitinib for retinal hemangioblastomas.
Renal cell carcinoma
Early surgery is the best option for renal cell carcinoma, although close monitoring is recommended for lesions <3 cm. Depending on the size and location of the tumor, nephron-sparing or partial nephrectomy may be possible without compromising survival [
Grubb et al 2005].
Nephrectomy should leave the adrenal gland in situ, as is done in individuals with renal cell carcinoma who do not have a confirmed diagnosis of VHL. If contralateral pheochromocytoma occurs, the remaining adrenal gland will prevent or delay steroid replacement therapy.
Cryoablation is being increasingly used for small lesions or in individuals who are likely to require multiple surgical procedures [
Shingleton & Sewell 2002].
Radio frequency ablation therapy is often applied to smaller tumors, particularly <3 cm [
Best et al 2012]. However, smaller lesions treated with radio frequency ablation need frequent intervention [
Joly et al 2011]. The major complication rate (need for a radiologic, surgical, or endoscopic intervention) for laparoscopic and percutaneous radio frequency ablation therapy was 7.3% and 4.3%, respectively [
Young et al 2012].
A recent study reported no complications after 19 radio frequency ablation treatments in individuals with VHL [
Allasia et al 2017].
Renal transplantation has been successful in individuals in whom bilateral nephrectomy has been necessary. It is imperative to evaluate any living related potential donor for VHL syndrome and to exclude those with VHL syndrome.
Pheochromocytomas
Pancreatic cysts and neuroendocrine tumors. Pancreatic cysts are common, rarely influence endocrine function, and have no malignant behavior. Therefore, surgical removal is not generally required [Sharma et al 2017].
Pancreatic neuroendocrine tumors need to be differentiated from cysts and serous cystadenomas. Pancreatic tumors are generally slow growing and are not hormonally active, although they can cause metastatic disease. Surgery should be strongly considered when there is a high risk of metastases, as suggested by one of the following prognostic criteria [Krauss et al 2018]:
Endolymphatic sac tumors (ELST). Consideration of surgical removal of these slow-growing tumors must include discussion of the possible complication of total deafness. Early intervention with small tumors has been shown to preserve both hearing and vestibular function [Friedman et al 2013]. Friedman et al described two individuals (2/18) with postoperative decreased facial nerve function and three (3/18) individuals with recurrent ELSTs (with a mean follow up of 67 months). Kim et al [2013] studied 31 individuals with VHL with 33 resected ELSTs; 29 individuals were symptomatic. After surgery, hearing was stabilized or improved in 97% of individuals, and tumor resection was complete in 91%. Complications occurred in three tumors: cerebrospinal fluid leakage in two (6%) and transient lower cranial nerve palsy in one (3%).
Epididymal or broad ligament papillary cyst adenomas generally do not require surgery, unless they are symptomatic or are threatening fertility.
Prevention of Secondary Manifestations
Early detection through surveillance and removal of tumors may prevent or minimize deficits such as hearing loss, vision loss, neurologic symptoms, and the need for renal replacement therapy.
Surveillance
Individuals with known VHL syndrome, individuals without clinical manifestations but identified as having a VHL pathogenic variant, and first-degree relatives who have not undergone DNA-based testing need regular clinical monitoring by a physician or medical team familiar with the spectrum of VHL syndrome:
Annual evaluation starting at age one year for neurologic symptoms, vision problems, or hearing disturbance
Annual examination starting at age one year for signs of nystagmus, strabismus, or white pupils
Annual blood pressure monitoring starting at age one year
Monitoring for complications is summarized in Table 3.
Table 3.
Monitoring for Complications in Individuals with von Hippel-Lindau Syndrome
View in own window
Complication | Evaluation | Frequency | Comment |
---|
CNS lesions | MRI of brain & total spine | Every 2 yrs starting at age 16 yrs 1 | Attention should be given to inner ear / petrous temporal bone (for ELST) & posterior fossa. |
Visceral lesions | Abdominal ultrasound | Annually starting at age 8 yrs | |
MRI scan of the abdomen (kidney, pancreas, & adrenal glands) | Every 2 yrs starting at age 16 yrs 1 | |
Retinal angiomas | Ophthalmology evaluation w/indirect ophthalmoscope | Annually starting at age 1 yr | |
Pheochromocytoma | Plasma or 24-hr urine for fractionated metanephrines | Annually starting at age 5 yrs | |
Endolymphatic sac tumors 2 | Recommended in symptomatic individuals: MRI w/contrast & high signal intensity w/T1 (to detect hydrops) using thin slices of the internal auditory canal | |
|
Audiology assessment | Every 2-3 yrs (annually if hearing loss, tinnitus, or vertigo is present) starting at age 5 yrs | Audiology can be used to detect (early) hearing loss. 4 |
ELST = endolymphatic sac tumors
- 1.
- 2.
The best way to detect ELST is unknown.
- 3.
- 4.
Binderup et al [2013b] described a male with demonstrable hearing loss by audiometric data whose ELST was only detectable with MRI more than one year later, after he already had complete right-sided hearing loss. Results from a large study on audiometric data in individuals with VHL are pending.
While current medical surveillance guidelines do not address structured psychological support for individuals with VHL, their partners, and their family members, research suggests a distinct need for psychosocial support [Lammens et al 2010, Lammens et al 2011b].
Note: The surveillance guidelines established for VHL are not evidence based and rely on experiential reporting, largely from North America. Guidelines may vary somewhat depending on the local standard of care.
In the United States, the VHL Alliance has worked extensively with health care professionals to assemble guidelines which are generally accepted throughout the world [VHL Handbook]. Other guidelines originate from Denmark and the Netherlands and may differ. For example: Dutch guidelines recommend screening for ELST only on indication, examination by a primary care physician and assessment of metanephrine levels starting at age ten years, and ophthalmologic examination beginning at age five years.
Two recent studies evaluated tumor progression. In one study, new tumor development was compared to age and genotype [Binderup et al 2013b]. According to their results, surveillance for retinal angiomas is essential during teenage years and CNS hemangioblastomas is mainly important in adults. In the other study, the optimal lesion-specific age to start surveillance and the optimal screening interval per organ system was analyzed [Kruizinga et al 2013]. The optimal time to start metanephrine measurements is age five years; retinal screening in individuals with VHL can start at age 12 years. For CNS hemangioblastomas and visceral lesions, starting age was in line with current surveillance guidelines. Furthermore, to attain a 5% detection rate, surveillance intervals for retinal tumors can be twice as long, and for the adrenal gland, four times as long.
Improved surveillance guidelines have increased the life expectancy of individuals with VHL by more than 16 years since 1990 [Wilding et al 2012]. Two studies evaluated the implementation of national surveillance guidelines in Denmark and the Netherlands. One study showed that more than 90% of the 84 affected individuals included reported that they were familiar with their national VHL surveillance guidelines. However, daily practice showed that 64% of those individuals had received information that was only partially consistent with the Dutch guidelines [Lammens et al 2011a]. In a Danish study, compliance and frequency of follow up was surprisingly low with regard to the national VHL guidelines for individuals with VHL and subjects at risk [Bertelsen & Kosteljanetz 2011]. These studies collectively suggest that correct implementation of surveillance guidelines through a doctor- and patient-oriented information campaign could have an immediate positive impact for individuals with VHL.
Agents/Circumstances to Avoid
Avoid the following:
Tobacco products, as they are considered a risk factor for kidney cancer
Chemicals and industrial toxins known to affect VHL-involved organs
Contact sports if adrenal or pancreatic lesions are present
Evaluation of Relatives at Risk
Early recognition of manifestations of VHL syndrome may allow for timely intervention and improved outcome; thus, clinical surveillance of asymptomatic at-risk individuals (including children) for early manifestations of VHL syndrome is appropriate. The American Society of Clinical Oncology identifies VHL syndrome as a Group 1 disorder – a hereditary disease for which genetic testing is considered part of the standard management for at-risk family members [Robson et al 2010] (full text).
If the VHL pathogenic variant in the family is known, molecular genetic testing can be used for early identification of at-risk family members to improve diagnostic certainty and reduce the need for screening procedures in those at-risk family members who have not inherited the pathogenic variant [Priesemann et al 2006].
If the VHL pathogenic variant in the family is not known and/or at-risk individuals decline genetic testing for religious or financial reasons, continued screening for VHL lesions is warranted (see Surveillance).
The use of molecular genetic testing for determining the genetic status of presumably at-risk relatives when a family member with a clinical diagnosis of VHL syndrome is not available for testing is not straightforward. Such test results need to be interpreted with caution. A positive test result signals the presence of a VHL pathogenic variant in the at-risk family member and indicates that the same molecular genetic testing method can be used to assess the genetic status of other at-risk family members. However, a negative test for a VHL pathogenic variant in an at-risk family member under such circumstances suggests one of the following possibilities:
The clinical diagnosis of VHL syndrome in the
proband is questionable.
In this situation, the presumably at-risk family member has a small, but finite, residual risk of having inherited a pathogenic allele (i.e., VHL syndrome or other hereditary disorder). In counseling such individuals, careful consideration should be given to the strength of the clinical diagnosis of VHL syndrome in the affected family member, the relationship of the at-risk individual to the affected family member, the perceived risk of an undetected VHL (or other gene) pathogenic variant, and the potential need for some form of continued clinical surveillance.
See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.
Pregnancy Management
Recommended medical surveillance for pregnant women with VHL is still debated. Research by the French VHL Study Group showed a significantly higher complication rate of hemangioblastomas in individuals with VHL who had had at least one pregnancy [Abadie et al 2010]. Another study concluded that pregnancy has a significant influence on cerebellar hemangioblastoma growth and causes an overall high complication rate (17%) [Frantzen et al 2012]. Intensified surveillance could therefore be recommended in a specialized medical center during preconception care and pregnancy. Special attention should be paid to pheochromocytoma and cerebellar hemangioblastoma. A recent study showed a decrease in new VHL manifestations during pregnancy [Binderup et al 2015]. In another study pregnancy did not correlate with the development of new hemangioblastomas or hemangioblastoma/cyst growth [Ye et al 2012]; the data suggested that no extra precautions need to be taken during gestation. The VHL Handbook recommends MRI of the cerebellum without contrast at four months' gestation.
Therapies Under Investigation
Certain VHL pathogenic variants fail to downregulate HIFα, leading to overexpression of downstream effectors such as vascular endothelial growth factor (VEGF) which contribute to pathogenesis. Many experimental therapies target these misregulated signaling pathways. An intravitreal VEGF receptor inhibitor, ranibizumab, has been used with some success in individuals with retinal hemangioblastomas who have either failed local therapy or whose lesions are not amenable to local therapy [Wong et al 2008]. Intravitreal injections of bevacizumab, another VEGF inhibitor, have also proven effective in treating retinal hemangioblastomas in individuals with VHL [Hrisomalos et al 2010]. Stabilization of some (but not all) CNS hemangioblastomas has also been demonstrated [Madhusudan et al 2004].
Sunitib, a tyrosine kinase inhibitor (TKI) that inhibits the action of VEGF receptors, has had some utility in the rare unresectable malignant pheochromocytomas, but simple surgical excision is clearly preferable for these usually benign tumors [Jimenez et al 2009]. Sunitinib has also been shown to effectively treat clear cell renal cell carcinomas – but not hemangioblastomas – in individuals with VHL [Jonasch et al 2011].
Pazopanib showed favorable effects on the clinical condition of individuals with recurrent and rapidly progressive VHL-associated hemangioblastomas [Migliorini et al 2015]. A pilot study to assess the safety and efficacy of another TKI, dovitinib, for the treatment of asymptomatic hemangioblastomas in individuals with VHL resulted in termination of the study after adverse events in all six individuals. Maculopapular rash, diarrhea, and fatigue were most common [Pilié et al 2018]. In a series of 22 individuals with VHL with a total of 311 lesions, good identification of VEGF-producing lesions suggest that (89)Zr-bevacizumab PET could offer a tool to select individuals for anti-VEGF therapy [Oosting et al 2016].
Somatostatin analogs could be of use in the treatment of hemangioblastomas. Nine hemangioblastomas demonstrated expression for at least three somastatin receptor subtypes (1, 2a, 3, 4, or 5). One individual with a symptomatic irresectable suprasellar hemangioblastoma was treated with octreotide long-acting release, which resulted in clinical stability and radiographic response after nine months of treatment [Sizdahkhani et al 2017].
Propranolol could be an efficient treatment to control hemangioblastoma growth in individuals with VHL because of its antiangiogenic effects demonstrated in infantile hemangioma and the hypothetic impact on HIF levels.
Checkpoint inhibitors such as antibodies targeting PD-L1 have shown promise in managing tumor load; however, these treatments have unknown toxicity in individuals with VHL, who will likely have dozens to thousands of small subclinical lesions present throughout their body.
Sardi et al [2009] reported three-year stabilization of previously progressive multifocal spinal hemangioblastomas with thalidomide.
Premature termination codon 124 (PTC124), also known as ataluren, may benefit a subset of affected individuals in whom nonsense variants give rise to premature stop codons in the messenger RNA [Auld et al 2010]. There are three stop codons: UAA, UAG, and UGA. PTC124 promotes read-through of all three stop codons with different efficiencies. The highest read-through efficiency takes place at UGA, followed by UAG and then UAA. PTC124 has been successfully proven to promote read-through of nonsense variants in Duchenne muscular dystrophy (DMD), cystic fibrosis (CF), and Usher syndrome type 1C. Phase I and II clinical trials have shown no serious side effects with PTC124 treatment, even after long-term use [Wilschanski et al 2011]. Preclinical investigation of PTC124 effects on VHL is ongoing.
An in vivo study of HIF2a inhibitor in vhl-/- zebrafish showed promising results in suppressing erythrocytosis and abnormal vascular proliferation in the brain and trunk. Furthermore, it promoted erythroid differentiation and decreased the number of early erythroid progenitors circulating in the peripheral blood. Therefore, there is a rationale for performing preclinical and clinical studies in optimized HIF2A inhibitors [Metelo et al 2015].
Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions.
Genetic Counseling
Genetic counseling is the process of providing individuals and families with
information on the nature, mode(s) of inheritance, and implications of genetic disorders to help them
make informed medical and personal decisions. The following section deals with genetic
risk assessment and the use of family history and genetic testing to clarify genetic
status for family members; it is not meant to address all personal, cultural, or
ethical issues that may arise or to substitute for consultation with a genetics
professional. —ED.
Mode of Inheritance
Von Hippel-Lindau (VHL) syndrome is inherited in an autosomal dominant manner.
Risk to Family Members
Parents of a proband
Sibs of a proband. The risk to the sibs of the proband depends on the clinical/genetic status of the proband's parents:
If a parent of the
proband is affected and/or has the
VHL pathogenic variant, the risk to the sibs of inheriting the variant is 50%.
If the parents have not undergone
molecular genetic testing but are clinically unaffected and are at least age 35 years, the risk to the sibs of a
proband appears to be low; however; the sibs are still at increased risk for VHL syndrome because of the possibility of failure to recognize the disorder or late onset of the syndrome in an affected parent.
Offspring of a proband. Each child of an individual with VHL syndrome is at a 50% risk of inheriting the VHL pathogenic variant; the degree of clinical severity is not predictable.
Other family members. The risk to other family members depends on the status of the proband's parents: if a parent is affected and/or has the VHL pathogenic variant, the parent's family members may be at risk.
Related Genetic Counseling Issues
See Management, Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.
Genetic cancer risk assessment and counseling. For a comprehensive description of the medical, psychosocial, and ethical ramifications of identifying at-risk individuals through cancer risk assessment with or without molecular genetic testing, see Cancer Genetics Risk Assessment and Counseling – for health professionals (part of PDQ®, National Cancer Institute).
Testing of at-risk asymptomatic family members. Molecular genetic testing of at-risk family members is appropriate in order to determine the need for continued clinical surveillance. Interpretation of molecular genetic test results is most accurate when a germline VHL pathogenic variant has been identified in an affected family member (see Evaluation of Relatives at Risk).
Because early detection of at-risk individuals affects medical management, testing of asymptomatic individuals during childhood is beneficial [Binderup et al 2013a) [VHL Handbook]. As ophthalmologic screening for those at risk for VHL syndrome begins as early as possible, certainly before age five years, molecular genetic testing may be considered in young children. Molecular genetic testing may be performed earlier if the results would alter the medical management of the child.
Parents often want to know the genetic status of their children prior to initiating screening in order to avoid unnecessary procedures in a child who has not inherited the pathogenic variant. Special consideration should be given to education of the children and their parents prior to genetic testing. A plan should be established for the manner in which results are to be given to the parents and their children. The authors recommend the VHL handbook for children by the VHL Alliance (VHL Handbook - Kids' Edition).
Other issues to consider. It is recommended that physicians ordering VHL molecular genetic testing and individuals considering undergoing testing understand the risks, benefits, and limitations of the testing prior to sending a sample to a laboratory. A study demonstrated that for almost one third of individuals assessed for familial adenomatous polyposis, an autosomal dominant colon cancer disease, the physician misinterpreted the test results [Giardiello et al 1997]. Referral to a genetic counselor and/or a center in which testing is routinely offered is recommended.
Considerations in families with an apparent de novo pathogenic variant. When neither parent of a proband has VHL syndrome and/or has the VHL pathogenic variant, the VHL pathogenic variant is likely de novo. However, possible non-medical explanations including alternate paternity or maternity (e.g., with assisted reproduction) or undisclosed adoption could also be explored.
Family planning
DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown). For more information, see Huang et al [2022].
Molecular Genetics
Information in the Molecular Genetics and OMIM tables may differ from that elsewhere in the GeneReview: tables may contain more recent information. —ED.
Table A.
Von Hippel-Lindau Syndrome: Genes and Databases
View in own window
Data are compiled from the following standard references: gene from
HGNC;
chromosome locus from
OMIM;
protein from UniProt.
For a description of databases (Locus Specific, HGMD, ClinVar) to which links are provided, click
here.
Gene structure.
VHL, which comprises three exons spanning ~10 kb of genomic DNA, is highly conserved among worms, flies, rodents, zebrafish, and humans [Kaelin 2002, Gossage et al 2015]. The full-length canonic transcript of ~4.5 kb is almost ubiquitously expressed and encodes protein isoforms of 213 (NP_000542.1) and 160-amino acid residues; the latter (also called VHLp19) results from initiation of translation from an internal methionine codon at position 54 and is the major product in most tissues. A rarer isoform lacking exon 2 (172 amino acids; NP_937799.1) does not function as a tumor suppressor but upregulates a subset of pro-tumorigenic genes including TGFB1, MMP1, and MMP13 [Hascoet et al 2017]. A VHL cryptic exon (termed E1') deep in intron 1 is naturally expressed in many tissues, and results in a 193-amino acid protein that contains the first 114 amino acids encoded by exon 1, followed by 79 additional amino acids of unknown function encoded by E1' [Lenglet et al 2018]. Proteomic analyses indicate that the isoforms have both distinct and overlapping interaction partners [Minervini et al 2015]. For a detailed summary of gene and protein information, see Table A, Gene.
Pathogenic variants. More than 500 germline pathogenic variants have been identified in families with von Hippel-Lindau (VHL) syndrome (see Table A) [Nordstrom-O'Brien et al 2010]. The spectrum of pathogenic variants reported includes 52% missense, 13% frameshift, 11% nonsense, 6% in-frame deletions/insertions, 11% large/complete deletions, and 7% splice site variants. Single-nucleotide variants have been identified in all three exons. The arginine codon 167 is considered a mutational "hot spot."
Synonymous pathogenic variants in VHL exon 2 that alter splicing through exon 2-skipping are associated with erythrocytosis or VHL disease in five families [Lenglet et al 2018].
Nordstrom-O'Brien et al [2010] describes detailed phenotype and pathogenic variant information for 945 families with VHL (see also Table A, Locus-Specific, HGMD, and ClinVar databases). The independent database VHLdb has linked 1,601 variants with protein interactions [Tabaro et al 2016].
VHL hypermethylation was identified at four sites in the promotor and 5'UTR in affected individuals from one family [Ma et al 2015]. No additional families with VHL hypermethylation have been identified.
Normal gene product. Von Hippel-Lindau syndrome tumor suppressor (pVHL) has been implicated in a variety of functions including transcriptional regulation, post-transcriptional gene expression, apoptosis, extracellular matrix formation, and ubiquitinylation [Kaelin 2007, Roberts & Ohh 2008, Gossage et al 2015]. The role of pVHL in the regulation of hypoxia-inducible genes through the targeted ubiquitinylation and degradation of HIF1α has been described, leading to a model of how disruption of VHL results in renal cell carcinoma, hemangioblastoma, and the production of other highly vascularized tumors.
Normal pVHL binds to elongin C (encoded by ELOC), which forms a complex with elongin B and cullin-2 (encoded by TCEB2 and CUL2, respectively), and Rbx1 (see ). This complex resembles the SCF ubiquitin ligase or E3 complex in yeast that catalyzes the polyubiquitinylation of specific proteins and targets them for degradation by proteasomes. The product of the gene RWDD3, RSUME (RWD domain-containing protein SUMO enhancer), sumoylates and binds pVHL, negatively regulating the assembly of this complex [Gerez et al 2015]. Under normoxic conditions, HIFα is hydroxylated at one of two specific proline residues, catalyzed by a member of the EglN family of prolyl hydroxylase enzymes.
Schematic view of pVHL and HIF A. Normoxia in a normal cell; HIF binds to pVHL.
The VHL protein then binds to hydroxylated HIFα and targets it for degradation. Under hypoxic conditions, HIF1α is not hydroxylated, pVHL does not bind, and HIF1α subunits accumulate. HIF1α forms heterodimers with HIF1β and activates transcription of a variety of hypoxia-inducible genes (i.e., VEGF, EPO, TGFα, PDGFβ, PDL1) [Messai et al 2016]. Likewise, when pVHL is absent or mutated, HIF1α subunits accumulate, resulting in cell proliferation and the neovascularization of tumors characteristic of VHL syndrome [Gossage et al 2015].
pVHL also has HIF-independent functions, such as regulation of aldehyde dehydrogenase 2 (ALDH2) and JunB transcription [Kanno et al 2012, Leisz et al 2015, Gao et al 2017].
Abnormal gene product. Pathogenic variants in VHL either prevent its expression (i.e., deletions, frameshifts, nonsense variants, and splice site variants) or lead to the expression of an abnormal protein (i.e., pathogenic missense variants). The type of VHL that results from a pathogenic missense variant depends on its effect on the three-dimensional structure of the protein [Stebbins et al 1999]. Pathogenic variants in VHL cause misfolding and subsequent chaperonin-mediated breakdown [Feldman et al 2003]. Pathogenic missense variants that destabilize packing of the alpha-helical domains, decrease the stability of the alpha-beta domain interface, interfere with binding of elongin C and HIF1α, or disrupt hydrophobic core residues result in loss of HIF regulation and are more likely to result in VHL type 1. Pathogenic missense variants that result in pVHL that is normal with respect to HIF regulation are more likely to be associated with VHL type 2 (see Genotype-Phenotype Correlations). Furthermore, VHL pathogenic variants affect vessel branching and maturation via the Notch signaling pathway [Arreola et al 2018].
Pathogenic missense variants that lead to pheochromocytoma with a low (or no) risk for RCC (types 2A and 2C) may encode a VHL protein that retains the ability to ubiquinate (and thereby downregulate) HIF1α in the presence of molecular oxygen to a greater degree than pathogenic variants that result in VHL syndrome with pheochromocytoma and RCC (type 2B). Furthermore, mutated pVHL may predispose to pheochromocytoma by altering the balance among a group of proteins in a molecular pathway that controls apoptosis of sympatho-adrenal precursor cells during development. Such cells may be at increased risk of developing into pheochromocytomas at a later stage [Lee et al 2005, Kaelin 2007].
Cancer and benign tumors. Acquired somatic pathogenic variants in VHL may give rise to sporadic VHL-type tumors (i.e., clear cell RCC and hemangioblastoma) [Iliopoulos 2001, Kim & Kaelin 2004] without other associated tumors characteristic of the hereditary syndrome. Tumors from the same patient have distinct somatic variant sets suggesting patient-specific factors (e.g., environmental) that drive or enhance tumorigenesis in addition to the germline VHL pathogenic variant [Fisher et al 2014, Fei et al 2016]. However, recent evidence also suggests that there is a haploinsufficient cellular environment prior to the somatic inactivation of the wild type allele that can promote dysplastic growth [Peri et al 2017].