[A Case of Bilateral Metachronous Breast Cancer with BRCA2 Genetic Mutation Discovered following Intramammary Hematoma Caused by Trauma].

The patient was a 56-year-old woman. At the age of 41, she underwent partial mastectomy and sentinel lymph node biopsy for right breast cancer. At the age of 55, she fell and bruised her left chest. An 8 cm subcutaneous hemorrhage and swelling was found in the left breast. We diagnosed intramammary hematoma and performed hemostasis and drainage of hematoma cavity. As she had undergone surgery for contralateral breast cancer, the possibility of a positive BRCA1/2 gene mutation was considered, and part of the inner wall of the hematoma cavity was removed during surgery and submitted for pathological tissue diagnosis. She was diagnosed with left breast cancer. Considering the possibility of HBOC, a BRCA1/2 genetic test was performed, which revealed a positive BRCA2 gene mutation. We performed an additional total mastectomy and sentinel lymph node biopsy. Breast cancer is often discovered during screening or when patients visit the hospital due to the feeling of a mass, but it is rare for it to be discovered through an intramammary hematoma. Here we report a case in which an intramammary hematoma following surgery for contralateral breast cancer was diagnosed as breast cancer based on histopathological examination of the inner wall of the hematoma cavity, in a patient who was highly likely to have a BRCA gene mutation.