Melanoma metastasis to the breast: A diagnostic pitfall

Background: Breast metastasis is an extremely rare phenomenon. While nearly every malignancy has been described to metastasize to the breast; melanoma, lymphoma and leukemia tend to be the most common. Among these primary tumors, melanoma metastasis represents a diagnostic pitfall for both the clinicians and histopathologists. Methods: We report a case of widely metastatic malignant melanoma with diagnostic difficulties in both clinical and histopathological evaluation. Thorax CT, Abdominal MRI, tumor marker screening and two biopsies were performed to conclude the primary. Results: In clinical evaluation, there were rapidly proliferating multiple nodular lesions at the skin, breasts, lungs, ovaries and peritoneum accompanied by only increased CA 125 in tumor marker panel. The initial biopsy performed from a skin nodule was concordant with a metastatic carcinoma suggesting breast as the primary. The diagnosis was made by immunohistochemical staining of the second biopsy performed from a breast nodule. Conclusion: Although no strict clinical criteria exist to differentiate a melanoma metastasis to the breast from a primary breast carcinoma atypically rapid growth, normal Ca 15-3 level, and a history of prior melanoma may be helpful. However, it may be still misdiagnosed in some cases even histopathologically if the immunohistochemical staining is not performed.