Dual genetic diagnosis of Lynch syndrome and hereditary breast and ovarian cancer as secondary findings in a cancer genomic profiling test for recurrent appendiceal carcinoma

Abstract

　The patient is a 64-year-old woman. Her mother and brother had colorectal cancer and her maternal uncle had gastric cancer. She was diagnosed as appendiceal cancer (pT4aN0M1c) with localized peritoneal dissemination at surgery and was treated with adjuvant chemotherapy. 18 months after surgery, she was diagnosed with bilateral ovarian metastases and peritoneal dissemination. Tumor-only cancer genomic profiling test revealed that the patient had tumor mutational burden-high and was eligible for pembrolizumab, but also had pathogenic variants in the MSH6 and BRCA2 genes. Genetic testing confirmed that both MSH6 and BRCA2 genes were pathological variants of germline origin, and the patient was dually diagnosed with Lynch syndrome and hereditary breast-ovarian cancer.

　With the spread of cancer genomic profiling tests, the number of cases of detection of hereditary diseases as secondary findings is expected to increase, but there are still few reports of dual genetic diagnosis, in which two hereditary diseases are detected simultaneously.