In the treatment of male breast cancer (MBC), it is essential to provide appropriate information on the genetic background of MBC. However, such information has not yet been thoroughly investigated. In this study, we experienced two cases of MBC that underwent genetic testing, and both showed the same pathogenic variant in germline BRCA2. Compared to women, MBC patients tend to have an older age of onset, hormone receptor-positive, invasive ductal carcinoma, and advanced cancer, which was also the case in these two cases. Both patients also had a family history of breast or pancreatic cancer, cancers associated with hereditary breast and ovarian cancer (HBOC). The variant found in the two cases was a relatively common variant previously suggested as a founder mutation in East Asian populations, including Japanese. It is helpful to provide information about HBOC to their relatives, especially their daughters, and promote appropriate measures, including genetic counseling. Even though genetic follow-up of blood relatives has not yet started even one year after disclosing the genetic results, highlighting the difficulty of sharing genetic information in MBC.

　Since Lynch syndrome (LS) takes the form of autosomal dominant inheritance, appropriate diagnosis and surveillance may enable early detection and treatment of cancer in the proband or their relatives. Early diagnosis of endometrial carcinoma is important for fertility preservation in women with LS. We report on two patients who were diagnosed with endometrial carcinoma in the early 30s in the middle of infertility treatment. They had MSH2 germline pathogenic variant. Both endometrial carcinomas were found in early stage, but total hysterectomy and postoperative adjuvant chemotherapy were required. It should be considered that their parents had not been diagnosed with LS, despite the treatment of LS-related tumors in our hospital. With appropriate diagnosis of LS and proper surveillance, it is possible that fertility-sparing treatment could have been performed with an earlier diagnosis of endometrial cancer. We realized again that the appropriate diagnosis of the proband could lead a significant impact on medical management, not only for the patient individual but also for the relatives.

　Angiosarcoma is one of the rare cancers and occurs mainly in the skin, soft tissue, breast, bone, liver, and spleen in adult, and partly in the great vessel and aorta. There are some reports of familial angiosarcoma, but none in Japan regarding familial or hereditary angiosarcoma. We experienced a case of angiosarcoma in siblings. The proband is a woman in her 40s. She was diagnosed with cardiac angiosarcoma at the age of 40. During her treatment, her brother was diagnosed with angiosarcoma in the liver at the age of 50. Some reports suggested that germline pathogenic variants of the POT1 gene are involved in the development of angiosarcoma. We report our case including the contents of genetic testing and literature review.

　Unresectable advanced pancreatic cancer using genetic testing of germline BRCA1/2 was performed, which was approved as companion diagnostics to determine the suitability of poly ADP-ribose polymerase (PARP) inhibitor．It may not be recognized that this testing is also used for the diagnosis of hereditary breast and ovarian cancer syndrome(HBOC)．We conducted genetic counseling for two cases of unresectable advanced pancreatic cancer cases with BRCA2 pathogenic variants．For case 1, a woman proband in her 60s was explained regarding HBOC twice before and after BRCA1/2 testing．A prostatic cancer was found in one of her relatives by family history．For case 2, the daughter and son of a male proband in his 60s visited after the result of his testing were disclosed．They were confused when they first learned that their father was diagnosed with HBOC, and have not been to the hospital since then．Genetic counseling is necessary even before testing and HBOC awareness should be shared among their relatives.

　The introduction of partial health insurance reimbursement for hereditary breast and ovarian cancer syndrome (HBOC) has resulted in an increase in the number of patients with breast cancer requesting BRCA1/2 genetic testing. In particular, patients who request this test for selecting an operative method for breast cancer require prompt implementation of the test, necessitating a review of our conventional genetic counseling (GC) system. In this report, we describe our efforts to address this issue and the experience of our first case in which preoperative BRCA1/2 genetic testing was performed as well as discuss future issues.