A 72-year-old woman was diagnosed with uveal melanoma, peritoneal mesothelioma and a primary biliary tract adenocarcinoma. She had a strong family history of mesothelioma as well as other malignancies including renal cell carcinoma. The recently described BAP1 hereditary cancer predisposition syndrome was suspected, but immunohistochemical labeling was not conclusive. Genetic testing confirmed a novel and unusual germline mutation in the ubiquitin hydrolase domain of the BAP1 gene (p.Tyr173Cys) and the patient was diagnosed with the BAP1 hereditary cancer predisposition syndrome. This case demonstrates the importance of clinically recognizing this rare syndrome and its manifestations, some which are still being characterized. It also highlights the importance of genetic testing in cases where there is a high clinical suspicion, even when screening tests, such as immunohistochemistry, in this case, are inconclusive. The diagnosis of a germline BAP1 mutation may have important implications for both the patient and their families with regards to further genetic testing and active surveillance programs. Further research is needed to fully understand the extent and clinical implications of this rare cancer syndrome.