Cytokeratin expression of apocrine and eccrine poromas with special reference to its expression in cuticular cells.

Abstract

There are no immunohistochemical studies on cytokeratin (CK) expression in large series of cases of apocrine poroma. In addition, detailed immunohistochemical analysis of cuticular cells, a specific type of constituent cells of poromas, has not been reported. Using the avidin-biotin method, we compared immunostaining patterns of eleven different anti-CK antibodies in 12 cases of apocrine and 21 cases of eccrine poromas, and normal adult skin. Poroid cells were exclusively positive for CK1/5/10/14, CK5/8 and CK14, which were expressed in the outer cells of normal dermal sweat ducts. Poroid cells were heterogeneously stained with anti-CK7, CK8/18, CK 10/11 and CK19 antibodies, which reacted in the inner cells of dermal ducts and in the secretory cells of sweat glands. The cuticular cells showed constant expression of CK1/5/ 10/14 and CK10/11, and various expression patterns of CK5/8, CK6, CK7, CK14, CK8/18, CK17, and CK19. Based on the keratin immunohistochemistry, the neoplastic cells in eccrine and apocrine poromas are considered to be closely related to the cells of dermal sweat ducts. Also the cuticular cells are considered to occupy an intermediate spectrum between the inner and outer cells of the dermal ducts. Although it is difficult to differentiate apocrine poroma from eccrine poroma by keratin expression patterns alone, the data obtained here can be helpful in differentiation of apocrine poroma from other hair follicle-related neoplasms.