A case of hidroacanthoma simplex

There are many conditions characterized by nests of cells within the epidermis. One of them, hidroacanthoma simplex, has been regarded as an epidermal tumor differentiating to intraepidermal eccrine duct cell. We report a case of hidroacanthoma simplex with the results of immunohistochemical study. Staining for 35 beta H11 (reacting with keratin No. 8), 35 beta E12 (reacting with keratin No. 1, 5, 10, 11), S-100 protein, and CEA was negative in the tumor cell nests; these monoclonal antibodies stained the nests of eccrine poroma.