Issues of concern in risk assessment, genetic counseling, and genetic testing of younger breast cancer patients in Japan.

About 5-10 % of breast cancer cases are considered to be hereditary, and germ line mutations in the BRCA1 and BRCA2 genes have been proven to contribute to the development of hereditary breast and/or ovarian cancer syndrome (HBOC). Breast cancer diagnosed at a young age is an indication of a higher likelihood of HBOC. Risk assessment, genetic counseling, and BRCA1/BRCA2 mutation testing, especially for younger women with breast cancer, have started to be an integral element of practice due to advances in gene sequencing technologies and accumulating evidence for the clinical implications of BRCA mutation status for not only early breast cancer management, but also for the patient's own and their family's next cancer risk, and proactive steps toward a risk-reducing approach. As yet, the cancer genetic service system is immature in Japan. There are several problems to be solved to improve cancer genetic services in clinical practice for breast cancer.