Tumor infiltrating the skin in the left pectoral region of a 54-year-old man was excised and examined. The paraffin embedded sections were stained by standard methods and immunohistochemical techniques. Histomorphology and Ímmunohistological phenotypization indicated either mammary adenocarcinoma or adnexal adenocarcinoma from sweat glands or metastasis. The definite diagnosis confirming mammary ori-gin was made on the basis of thorough evaluation of all flndings including exact clinical history. Authors review personál and literary experience that could help to distinguish skin infiltrating adenocarcinomas in routine biopsy practice.

        Key words: adenocarcinoma - differential diagnosis - immunohistochemistry