[A Case of Early-Onset Breast Cancer for Which the Operative Indication for Breast Conservation Was Based on BRCA Genetic Testing].

We report a case of a patient with early-onset breast cancer who decided to undergo adaptation for breast-conserving surgery based on the results of genetic testing. A 25-year-old woman became aware of a lump in her left breast and visited a nearby hospital, where she was diagnosed with breast cancer. She has no personal history. Her paternal grandfather was diagnosed with rectal cancer at age 60. Ultrasonography revealed an irregularly-shaped hypoechoic mass measuring 3.8 cm in the C area of her left breast and an enlarged lymph node 2.0 cm in diameter in the left axillary area. The breast tumor was pathologically diagnosed as invasive ductal carcinoma by core needle biopsy and was immunohistochemically characterized as ER(-), PgR(-), and HER2(-), s o-called triple negative. Moreover, lymph node metastasis was confirmed by fine needle aspiration cytology. She underwent neoadjuvant chemotherapy and achieved a clinical complete response. A woman with early-onset triple negative breast cancer has a high probability of hereditary breast and ovarian cancer, with a high risk of ipsilateral second breast cancer after conserving surgery. Thus, BRCA genetic testing may be necessary before surgery. As no pathogenic mutation wasfound in BRCA 1/2 in this case, the patient underwent breast-conserving surgery followed by radiation therapy for the conserved breast. The patient remained healthy and without any recurrence 4 years and 2 months after surgery.