Lipomatous meningioma: Case report and review of the literature

Abstract

1. Introduction

Lipomatous meningiomas are a very rare variety of meningioma where adipocytes and lipoblasts contribute to fat accumulation within the tumor (see Table 1).^[1] The mean age for lipomatous meningioma presentation is 50 years of age with a range from 22 to 74 years reported in the literature.^[2] These tumors are a subgroup of a broader class termed “metaplastic meningiomas” that has been proposed by the World Health Organization.^[3] It is a variant, which contains mesenchymal components including osseuous, cartilaginous, lipomatous, myxoid and xanthomatous tissue.^{[1, 3]} Characteristic of lipomatous meningiomas are intratumoral fat accumulations, which are best appreciated on computerized tomographic (CT) as hypodense and on T1-weighted magnetic resonance imaging (MRI) as hyperintense lesions.^[4] Definitive diagnosis requires histopathologic evaluation and cannot be based on imaging findings alone.^[5] In the case of intracranial lesions; the standard of care is craniotomy with tumor excision followed by histopathologic evaluation of the resected tissue.^[6] We present a case of a 58-year-old woman with a history of migraines that was found to have a right parietal lipomatous meningioma, and a Simpson grade I resection was performed. We provide a detailed review of the literature and provide relevant discussion of key clinical considerations for managing patients with lipomatous meningiomas.

2. Case

The patient is a 58-year-old female who presented in early June 2016 with main complaint of right-sided headache. She had been referred by an outside facility for a history of an enlarging submental mass starting in May, and a finding of a right parietal homogenously enhancing mass. Her past medical history included basal cell carcinoma on her cheek that was excised, migraines, left arm numbness, forgetfulness. Other significant conditions include a history of depression, reflux, hypertension, inflammatory bowel disease, and diverticulosis. There was no history fever or weight loss on presentation. On physical exam her body mass index (BMI) was 38.9 kg/m² and lymphadenopathy was noted in the submental area. The remainder of her history and physical exam was non-contributory. CT brain revealed two hypodense lesions in the right parietal measuring 2.6 cm × 2 cm and left parietal measuring 1.4 cm × 1 cm and MRI showed hyperintensity of the lesions on T1-weighted sequence, along with contrast enhancement on T1 + Gadolinium. In addition, gradient echo sequence (GRE) revealed presence of blood products (see Figure 1).

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Figure 1

Brain CT

(A) Non-contrast CT axial demonstrated a hypodense mass with calcifications in the right parietal lobe; (B) T2-weighted axial view demonstrated mixed intensity of the mass; (C) Gradient echo sequence (GRE) demonstrated susceptibility consistent with blood products (D) T1-weighted axial view demonstrated hyperintense signal of the mass (E) T1-weighted Gd-enhanced axial view demonstrated contrast enhancement of the mass; (F) T1-weighted Gd-enhanced axial view of the left parietal mass demonstrated contrast enhancement.

CT of the chest, abdomen, and pelvis with and without contrast was ordered. The CT scan revealed bilateral hypodense renal masses and hypodensity within the spleen that were not concerning for malignancy. Based on the imaging results, an ultrasound core biopsy of the submental lymph node was scheduled and performed. The biopsy results showed a reactive lymph node with no evidence of malignancy. After discussing the results with the patient, she underwent a right retrosigmoid craniotomy for Simpson grade 1 tumor resection. On gross pathology, the tumor was pink, rubbery, and hemorrhagic. Microscopically, the tumor demonstrated a mixture of meningothelial lobules and adipocyte-like cells consistent with lipomatous meningioma (see Figure 2). The patient recovered well post-surgery and was discharged on post-operative day 3. At her 1-month postoperative visit, her headache had resolved. The excisional site was without drainage or infection.

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Figure 2

H&E staining

(A) H&E, 10× shows mixture of meningothelial lobules and adipocyte-like cells; (B) H&E, 20× shows meningothelial lobules with larger adipocyte-like cells and cells with prominent lipid accumulation (upper right).

3. Discussion

The underlying pathophysiology of lipomatous meningiomas has been debated. Though initially thought to involve the metaplasia of meningothelial cells to adipocytes,^[7] several authors have attributed the alteration to fat accumulation due to disrupted metabolism within meningothelial cells.^{[1, 8]} The cells are typically positive for histologic markers including epithelial membrane antigen, vimentin and CD68. The hallmark finding however is the presence of adipocyte-like cells, which were noted in the histopathologic specimen from our patient.^[9] Savardekar and colleagues found that these lipomatous areas are readily visible with standard MRI protocols.^[10] In our particular case, there was no evidence of a dural tail sign on T1 + Gadolinium which is not unusual as a dural tail sign is only present in 52%–78% of meningiomas.^[14] Once the lesion was identified in our patient, a CT of the chest, abdomen, and pelvis was performed to rule out metastatic disease.

Fortunately, lipomatous meningiomas are most often WHO grade I, typically slow growing, are not metastatic, and do not require chemotherapy or radiation following resection.^[15] Following gross total resection, they exhibit low recurrence. Only 17% of lipomatous meningiomas recurred in the case series by Roncaroli and colleagues.^[1] When identified with appropriate imaging, complete resection is readily obtainable in the vast majority of cases.^[6] A Simpson grade I was achieved in our patient with excellent recovery post-surgery with limited residual symptoms. We chose to operate on the right side, as the patient appeared to be symptomatic from this lesion given her right-sided headaches, in addition, we strategies for the small left parietal lesion. would obtain tissue pathology that would guide treatment

Symptom manifestation for lipomatous meningiomas is variable depending on size and location of the tumor. The majority of lipomatous meningiomas reported in the literature have been frontal or frontotemporal in origin with only a few being parietal.^[11] Seizures are the most common manifestation for frontal and frontotemporal tumors, while headaches are more common for parietal tumors.^{[12, 13]} Our patient had a history of migraine headaches, which may have been the result of her slowly growing lipomatous meningioma. Another rare finding is that lipomatous meningiomas can sometimes manifest as behavioral disturbance in patients.^[8] Our patient had a history of both depression and forgetfulness.

4. Conclusions

Lipomatous meningiomas are a rare variety of meningiomas that are WHO grade I. Suspicion for this type of tumor should be high for patients with seizures, headaches, or behavioral changes that have lipomatous characteristics on imaging with either CT or MRI. The identification of meningothelial lobules and adipocyte-like tumor cells after resection confirms the diagnosis.

Footnotes

References