[A case of malignant melanoma metastasis to the mammary gland].

Herein, we report a rare case of malignant melanoma metastasis to the mammary gland. A 76-year-old woman had a tumor resection performed for primary malignant melanoma of the epipharynx. The patient subsequently underwent local and lymph node recurrence, for which she received heavy ion radiotherapy and lymph node dissection, respectively. The patient was referred to our hospital for a problem with her right breast. Computed tomography and magnetic resonance imaging showed a mammary tumor and multiple subcutaneous tumors. A biopsy was performed, which proved positive for S100 and Melan A staining, and the diagnosis of malignant melanoma was confirmed. Partial mastectomy was performed; and S100, HMB45, and Melan A positivity was confirmed based on immunohistological findings. The diagnosis was malignant melanoma metastasis to the mammary gland. Malignant melanoma commonly metastasizes to the liver, mediastinum, mediastinal glands, lung, and brain; and metastasis to the mammary gland is rare. To our knowledge, only 2 cases have previously been reported in the Japanese literature.