[A Case of Malignant Lymphoma of the Breast after Treatment of the Contralateral Breast Cancer].

A 57-year-old female was referred to our hospital due to a palpable tumor of the left breast; she was diagnosed with cancer in the left breast 3 years prior, in 201X. After the administration of FEC and docetaxel plus trastuzumab as preoperative chemotherapy, left mastectomy with axillary lymph node dissection was performed, and irradiation and trastuzumab were administered postoperatively for 1 year. During the observation, there was skin thickening around the right nipple. A skin biopsy was then performed in 201X, and the patient was diagnosed with diffuse large B-cell lymphoma(DLBCL). PET-CT revealed a slight accumulation in the peripheries of the right nipple and mammary glands. Core needle biopsy of the tumor in the mammary gland showed DLBCL similar to that observed in the skin biopsy. Imaging revealed complete response after chemotherapy, whole-body irradiation, and intrathecal administration. Currently, both breast cancer and DLBCL of the breast have not relapsed.