A Rare Case of Male Breast Cancer Presenting as a Superficial Pigmented Nipple Tumor: The Importance of a Deep Excisional Biopsy and Immunohistochemical Analysis in Diagnosis.

Nipple lesions present diagnostic challenges due to overlapping clinical and histopathological features. A 65-year-old male presented with a black skin lesion on his right nipple, initially suspected to be malignant melanoma. Dermoscopy suggested basal cell carcinoma, while punch biopsy findings indicated sweat gland carcinoma with negative mammaglobin staining. However, total resection revealed cord-like invasion into the deep dermis near the mammary gland, and immunohistochemistry showed mammaglobin positivity, leading to a final diagnosis of solid-type invasive ductal carcinoma of the breast. This case highlights the diagnostic challenges of male nipple tumors and underscores the need for thorough histopathological and deep-layer assessment to distinguish breast cancer from cutaneous malignancies.