A Japanese case of familial malignant melanoma with germline CDK4 variant incidentally diagnosed by cancer genome profiling.

Familial malignant melanoma (FMM) is a hereditary tumor that is quite rare in Japan; to date, the germline CDK4 variant has scarcely been reported around the world. Thus, we report on a woman with FMM who developed salivary gland cancer, for which a germline pathogenic variant of CDK4 was incidentally identified through comprehensive genomic profiling. She had a history of multiple atypical nevi and a facial melanoma since her 30 s and multiple family histories of melanoma; however, none of her relatives were aware of its heredity. Genetic counseling and skin surveillance were performed. Precision medicine for cancer can discover this rare genetic syndrome and provides us with the opportunity to manage the health of patients and their relatives.