Invasive ductal carcinoma of the breast associated with extensive melanin melanosis: a case report and review of the literature.

Extensive melanosis of breast tissue due to melanin in the absence of involvement by melanoma either primary or secondary has been rarely encountered. Herein we report a first and unique case of extensive macroscopic and microscopic melanosis of mammary parenchyma between carcinoma cells due to melanin in a patient with a poorly differentiated invasive ductal carcinoma of the breast with no evidence of melanocytic differentiation or melanoma. In contrast to previously reported cases in the literature, there is no breach of dermal-epidermal junction and there is no dermal infiltrate in the skin overlying the carcinoma, or Pagetoid disease in the nipple.