Malignant melanomas arising in the skin, buccal mucous membranes. and retina are encountered frequently. A malignant melanoma characteristically disseminates widely but infrequently metastasizes to the breast, and primary melanoma of the breast is even rarer. Primary melanomas can arise in the glandular tissue of the breast. We report a case of malignant melanoma either primary in the breast or metastatic from an unknown primary that presented initially as a left breast mass without a detectable cutaneous lesion.