Among patients carrying pathogenic or likely pathogenic BRCA1/2 mutations, reversion mutations in BRCA1/2 genes were seen in ovarian cancer (OC) (30/3424), breast cancer (BC) (27/1460), endometrial cancer (4/564), pancreatic cancer (2/340), cholangiocarcinoma (2/178), prostate cancer (5/461), cervical cancer (1/117), cancer of unknown primary (1/244), bladder cancer (1/300), malignant pleural mesothelioma (1/10), and a neuroendocrine tumor of the prostate. The gene discussed is BRCA1; the disease is ovarian cancer.