Adenocarcinoma with signet ring cells of the axilla showing apocrine features: a case report.

A 74-year-old Japanese man developed a reddish, indurated plaque composed of multiple nodules on his right axilla. Histopathologic examination showed a solid tumor that extended from the upper dermis into the subcutis, with both inter- and intracellular lumen formation, cellular arrangement in single files, a fibrotic reaction around the tumor cells, and the presence of mucinous material in the cytoplasm. There was both nuclear and cytoplasmic pleomorphism. Both lysozyme and GCDFP-15 were identified in the tumor cells. Electron microscopic examination showed periluminal condensation of the cytoplasm. Because thorough clinical and laboratory examinations were unremarkable, we regarded this to be a case of primary adenocarcinoma with signet ring cells of the axilla. The neoplasm might have differentiated toward the apocrine sweat glands or the mammary glands. Radiation therapy was effective to some degree. This seems to be the first reported case in which adenocarcinoma with signet ring cells of the skin affected a site other than the eyelids.