Tumors with Definitive Evidence of Association with BAP1-TPDS
BAP1-inactivated melanocytic tumor (BIMT; formerly called atypical Spitz tumor). The natural history of these lesions is not clearly known. It appears that individuals with BAP1-TPDS typically have multiple lesions [Haugh et al 2017]. BIMT are skin colored to reddish brown, averaging 5 mm in diameter; the histologic findings are between those of a Spitz nevus and a melanoma. Both copies of BAP1 are inactivated, leading to loss of staining for the BAP1 protein on immunohistochemistry; in addition, BIMT usually have the somatic BRAF pathogenic variant p.Val600Glu.
Uveal melanoma (UM) is the most commonly reported cancer in persons with BAP1-TPDS (36% of probands and 16% of relatives reported with BAP1-TPDS have UM), and it is the cancer with the earliest reported age of diagnosis (age 16 years) [Walpole et al 2018]. However, many of the earlier studies on BAP1 were investigating those with UM and familial UM, so selection bias may have contributed to the higher observed frequency of UM [Turunen et al 2016, Rai et al 2017, Repo et al 2019, Singh et al 2021]. Studies of unselected individuals with cancer show lower frequency of UM in those with BAP1-TPDS [M Abdel-Rahman et al, unpublished data]. Median age of onset of UM in persons with BAP1-TPDS is 50.5 years, which is younger than the onset of UM in the general population (age 62 years) [Singh et al 2021]. The tumors are generally more aggressive class 2 (i.e., high metastatic risk) tumors with reduced survival [Njauw et al 2012, Rai et al 2016]. In one study, mean length of survival in persons whose UM lacked BAP1 expression was 4.74 years compared to 9.97 years in persons whose tumors expressed BAP1 [Kalirai et al 2014].
Malignant mesothelioma (MMe) is the second most frequent cancer (25% of probands and 19% of relatives) identified in individuals with BAP1-TPDS [Walpole et al 2018]. Several studies have shown that the median age of onset of MMe in individuals with BAP1-TPDS was significantly earlier (age 55-58 years) than that of sporadic MMe (age 68-72 years) [Baumann et al 2015, Ohar et al 2016, Walpole et al 2018]. In the general population, pleural MMe accounts for about 80% of MMe and peritoneal MMe constitutes most of the remaining MMe. However, in individuals with BAP1-TPDS the ratio of peritoneal to pleural involvement is significantly higher [Carbone et al 2015, Cheung et al 2015, Ohar et al 2016, Walpole et al 2018]. Additionally, in BAP1-TPDS the majority of peritoneal MMe occurs in women, in contrast to the general population, in which men are more likely to have this tumor type [Walpole et al 2018].
In contrast to survival in persons with BAP1-related CM, UM, or RCC, survival in persons with BAP1-related MMe may be significantly longer than in the general population, especially in those with pleural mesothelioma [Baumann et al 2015, Pastorino et al 2018, Wang et al 2018, Hassan et al 2019, Carbone et al 2022].
Growing evidence suggests that BAP1 pathogenic variants interact with environmental asbestos exposure to increase the risk for MMe [Xu et al 2014, Kadariya et al 2016].
Cutaneous melanoma (CM). First reported in association with BAP1-TPDS in 2011, CM is now known to be the third most common cancer in BAP1-TPDS, occurring in 13% of affected individuals [Wiesner et al 2011]. Interestingly, Walpole et al [2018] found CM in 45% of probands but in no relatives affected with BAP1-TPDS [Walpole et al 2018]. Multiple primary cutaneous melanomas are common in BAP1-TPDS. The median age of onset of CM in individuals with BAP1-TPDS is earlier than in the general population (age 39 vs 58 years). While it is possible that BAP1-related CM is more aggressive than CM in the general population, the data are currently inconsistent [Gupta et al 2015, Kumar et al 2015, Rai et al 2016, Liu-Smith & Lu 2020].
Renal cell carcinoma (RCC). Heterozygous BAP1 germline pathogenic variants are specifically associated with an increased risk for RCC, in particular those with clear cell morphology [Haas & Nathanson 2014]. Walpole et al [2018] found RCC in 10% of probands and relatives with BAP1-TPDS, although the specific histology was not always known and additional morphologies, including papillary and chromophobe cell tumors, were also observed. Median age of RCC diagnosis appears to be younger in persons with BAP1-TPDS than in the general population (age 47-50 vs 64 years) [Rai et al 2016]. RCC with BAP1 pathogenic variants (somatic or germline) is associated with a higher grade and worse prognosis in both localized and advanced stages [Hakimi et al 2013, Kapur et al 2013, Joseph et al 2014].
Basal cell carcinoma
(BCC) has been confirmed as a tumor in the BAP1-TPDS spectrum [de la Fouchardière et al 2015b, Mochel et al 2015, Wadt et al 2015]. Multiple primary basal cell carcinomas are common. Walpole et al [2018] found that the median age of diagnosis for non-melanoma skin cancer (primarily BCC) was 44 years.
Meningioma, particularly a high-grade rhabdoid subtype, has been suggested to be associated with BAP1-TPDS [Abdel-Rahman et al 2011, Cheung et al 2015, de la Fouchardière et al 2015a, Wadt et al 2015, Shankar et al 2017]. This is further supported by identification of this tumor in 8.5% of probands with BAP1-TPDS and 2.2% of relatives with the BAP1 pathogenic variant [Walpole et al 2018].
Cholangiocarcinoma has also been suggested to be part of BAP1-TPDS [Njauw et al 2012, Pilarski et al 2014, Wadt et al 2015]. Walpole et al [2018] found this cancer in 1.4% of probands with BAP1-TPDS but in none of the relatives with the BAP1 pathogenic variant. Cholangiocarcinoma was observed in 3/42 of an unselected cancer cohort [M Carlo et al, unpublished data] and in 3/138 of individuals with BAP1-TPDS [M Abdel-Rahman et al, unpublished data] with evidence of BAP1 biallelic inactivation in tumors.
Tumors with Moderate Evidence of Association with BAP1-TPDS
Hepatocellular carcinoma (HCC). Germline BAP1 pathogenic variants have been observed in 0.5% of unselected individuals with HCC [Huang et al 2018]. Walpole et al [2018] identified HCC in 0.7% of probands with BAP1-TPDS and 1.6% of relatives with the BAP1 pathogenic variant.
Ovarian sex cord-stromal tumor. One individual with an ovarian sex cord-stromal tumor had a BAP1 germline pathogenic variant and BAP1 loss in tumor tissue [Albright et al 2023]. Three additional individuals with ovarian sex cord-stromal tumor and germline BAP1 pathogenic variants were observed in another cohort; somatic BAP1 biallelic inactivation was observed in two of the tumors [M Abdel-Rahman et al, unpublished data].
Onychopapilloma. Clinical findings consistent with onychopapilloma were detected in 39/47 individuals (83.0%), including 35 of 40 individuals age 30 years or older (87.5%). Nail bed biopsy was performed in five individuals and was consistent with onychopapilloma. Polydactylous involvement with onychopapillomas was detected in nearly all individuals who had nail involvement (38/39 individuals [97.4%]) [Lebensohn et al 2024].
Note: Nail abnormalities are also reported. A single-center prospective cohort study of 47 individuals with BAP1-TPDS reported a high prevalence of nail abnormalities (87.2%), including leukonychia, splinter hemorrhage, onychoschizia, and distal nail hyperkeratosis [Lebensohn et al 2024].