The expression of cytokeratins in 10 cases of clear cell
hidradenoma, including 3 cases of
solid cystic hidradenoma, were examined using 21 kinds of
monoclonal antibodies. We divided them into three histologic patterns: massive nests with a few lumina (M nests), nests with some tubular lumina (L nests), and nests in
solid cystic hidradenomas (S nests). All
hidradenomas showed similar immunoreactivities to those in the lower dermal ducts or secretory cells of normal eccrine glands. With
antibodies against simple epithelial cytokeratins (CKs 7, 8, 18, and 19), however, different immunostaining was noted among the three histologic patterns. Namely, the M nests failed to react to them, although some
luminal cells in the L nests revealed a positive staining. Furthermore, a majority of
luminal cells in the S nests revealed a positive staining with them. Therefore, we think that the
luminal cells in
solid cystic hidradenoma mainly differentiate toward the secretory cells, and that the M nests mainly differentiate toward the dermal duct. Those in the L nests are thought to differentiate toward the dermal duct and the secretory cells. The proportion of the differentiation toward
luminal cells of dermal ducts to the differentiation toward secretory cells was the main difference among the three nests. In addition, there was no difference in immunophenotypes between clear cells and epidermoid cells in the two kinds of
hidradenomas.