Melanocyte colonization and pigmentation of breast carcinoma.

Colonization of mammary cancers by melanocytes with attendant pigmentation of cancer cells by melanin occurs in most cases of breast cancer in which the dermal--epidermal interface is reached by the tumour cells. There is evidence to suggest that the mammary cancer may become colonized at the expense of the epidermis, which is focally depleted of melanocytes. Melanocytes can even be found in groups of tumour cells within lymphatics. Colonization and pigmentation of breast cancer is usually only easily detected by selective staining methods. In very rare cases it can be gross and easily detectable in routine stains. The implications of this migratory phenomenon are discussed in terms of the biology of the melanocyte.