Diagnostics of BAP1-Tumor Predisposition Syndrome by a Multitesting Approach: A Ten-Year-Long Experience

Germline mutations in the tumor suppressor gene BRCA1-associated protein-1 (BAP1) lead to BAP1 tumor predisposition syndrome (BAP1-TPDS), characterized by high susceptibility to several tumor types, chiefly melanoma, mesothelioma, renal cell carcinoma, and basal cell carcinoma. Here, we present the results of our ten-year experience in the molecular diagnosis of BAP1-TPDS, along with a clinical update and cascade genetic testing of previously reported BAP1-TPDS patients and their relatives. Specifically, we sequenced germline DNA samples from 101 individuals with suspected BAP1-TPDS and validated pathogenic variants (PVs) by assessing BAP1 somatic loss in matching tumor specimens. Overall, we identified seven patients (7/101, 6.9%) carrying six different germline BAP1 PVs, including one novel variant. Consistently, cascade testing revealed a total of seven BAP1 PV carriers. In addition, we explored the mutational burden of BAP1-TPDS tumors by targeted next-generation sequencing. Lastly, we found that certain tumors present in PV carriers retain a wild-type BAP1 allele, suggesting a sporadic origin of these tumors or a functional role of heterozygous BAP1 in neoplastic development. Altogether, our findings have important clinical implications for therapeutic response of BAP1-TPDS patients.