Hidroacanthoma simplex showing variation in the appearance of tumor cells in different nests

Differentiation of Hidroacanthoma Simplex from Clonal Seborrheic Keratosis-An Immunohistochemical Study

Hidroacanthoma simplex (HS) is an uncommon poroid neoplasm confined within the epidermis. The clinical features of HS are not distinctive and histopathologically HS may be confused with clonal seborrheic keratosis (CSK) if cystic or ductal structure is not present. The purpose of our study was to differentiate HS from CSK by the immunohistochemical expressions of various cytokeratins, CEA, CD1a, and S-100 protein, as well as by the degrees of deposition of melanins and glycogen. Four cases of HS and seven cases of CSK were included in the research. In contrast with CSK, HS showed a very low density of Langerhans cells (19.9 +/- 7.7 versus 3.1 +/- 1.0 CD1a (+) cells/mm, P = 0.027) and sparse melanin deposition in the nests. However, HS could not be set apart from CSK by the expressions of cytokeratins. The nests of both HS and CSK showed very similar patterns of cytokeratin expression and seemed to be mainly composed of basaloid cells with focal differentiation toward epidermal suprabasal cells.

A case of porocarcinoma from pre-existing hidroacanthoma simplex: need of early excision for hidroacanthoma simplex?

BACKGROUND

Hidroacanthoma simplex (HAS) is an uncommon eccrine neoplasm of the skin. It is a benign neoplasm, but some cases of malignant change were reported in the literature.

OBJECTIVE

To describe a rare case of porocarcinoma in a relatively short period from pre-existing HAS on the abdomen.

METHODS

Wide local excision was performed on this neoplasm.

RESULTS

There was no recurrence for 72 months after wide excision. CONCLUSION. : We recommend an early excision and careful attention in the case of HAS because of its potential malignant change.

Clear-cell porocarcinoma in situ: a cytologic variant of porocarcinoma in situ

Poromas are benign neoplasms composed of poroid and cuticular cells. Four histopathologic variants of poromas are accepted, according to the architectural features of the neoplasm: hidroacanthoma simplex or intraepidermal poroma; eccrine poroma, which is a poroma connected to the epidermis that extends to superficial dermis; dermal duct tumor, which develops when the neoplasm is composed of small, solid aggregations of poroid and cuticular cells confined to the dermis with little or no connection with the epidermis; and poroid hidradenoma, which is a solid-cystic, dermal poroma. The malignant counterpart of hidroacanthoma simplex is named malignant hidroacanthoma simplex or porocarcinoma in situ. This report describes an example of clear-cell malignant hidroacanthoma simplex, a cytologic variant of porocarcinoma in situ, which, to our knowledge, has not been previously reported. In contrast with other clear-cell neoplasms, a relation with diabetes mellitus could not be clearly established in this case.

Hidroacanthoma simplex: an ultrastructural and immunohistochemical study

A representative case of hidroacanthoma simplex was studied with routine light microscopy, immunohistochemistry, and electron microscopy. Staining with the periodic acid-Schiff reagent and immunostaining with anti-keratin antibodies were useful in demarcating the tumor cells from adjacent normal epithelium. However, antibodies to carcinoembryonic antigen and epithelial membrane antigen did not help us to segregate or identify the neoplastic cells. Electron microscopy revealed tumor cells markedly different in appearance from luminal cells of the acrosyringium. Hidroacanthoma simplex does not appear to be derived from luminal cells of the acrosyringium. We propose criteria for the histologic diagnosis of this benign neoplasm.