BRCA1 associated protein-1 (BAP1) cancer syndrome refers to a novel autosomal dominant cancer predisposition syndrome associated with the development of benign, atypical melanocytic tumors at a younger age and multiple malignancies, including mesothelioma, cutaneous and uveal melanoma, and other cancers, at an older age.

BAP1 is a deubiquitinase involved in regulating many important cellular functions, including cell death, cell cycle, DNA repair, and tumor suppression. Germline mutation causes a predisposition to tumor development. "BAP-omas," or melanocytic BAP1-mutated atypical intradermal tumors (MBAITs), are intradermal melanocytic lesions with onset in the second decade of life. Histologically, these lesions share features with atypical Spitz nevi and are notable for loss of BAP1 expression. Patients are also at risk for cutaneous and uveal melanoma. Despite minimal asbestos exposure, mesotheliomas develop around the fifth decade of life. Compared with conventional mesotheliomas, they tend to involve the pleura or the peritoneum equally, may be associated with prolonged survival periods of more than 5 years, and have a slight predilection for females. (Conventional mesothelioma typically occurs around the seventh decade of life, favors the pleura, has a male predominance, and carries a poor survival prognosis of less than 1 year.)

Other associated malignancies include basal cell carcinoma, renal cell carcinoma, meningioma, neuroendocrine tumor, paraganglioma, mucoepidermoid cancer, lung cancer, sarcomas, breast cancer, cholangiocarcinoma, colorectal cancer, ovarian cancer, prostate cancer, and thyroid cancer.