Metastasis of malignant melanoma (MM) to the breast is very rare, accounting for only 1.3% to 2.7% of all melanoma cases. In addition, many are metastases to the skin and subcutaneous tissue of the breast, and metastasis to the breast parenchyma including the mammary gland is even rarer, with a very limited number of reports. A 47-year-old female presented with a lump in the lower-outer quadrant of the right breast noted 6 months prior. Visual examination and palpation, ultrasonography, and mammography were performed. The skin of both breasts showed no abnormal findings and no melanoma. Core needle biopsy (CNB) was performed. The result of CNB was malignant melanoma. Metastasis from other sites was considered more likely than primary malignancy of the breast. A 10 × 12 mm melanoma lesion on the right upper arm had shown progressive growth over 1.5 years. The lesion on the right upper arm was considered the primary lesion. Positron Emision Tomography-Computed Tomography (PET-CT) detected a nodule in the left upper lobe of the lung, and metastasis of MM was suspected. The right breast tumor was resected. Histopathological results were pT3N0M1, Stage IV. BRAF mutation was negative. Nivolumab + ipilimumab was scheduled for further treatment.

Malignant melanoma, Metastasis, Breast