Poroid hidradenoma: a light microscopic and immunohistochemical study.

Poroid hidradenoma is a recently described variant of the eccrine poroma group of tumors. This neoplasm shows architectural characteristics of hidradenoma (tumor cells confined entirely within the dermis in both solid and cystic components) and cytologic characteristics of poroid neoplasm (poroid and cuticular cells, the latter showing ductal differentiation). Therefore the term "poroid hidradenoma" seems to be the most appropriate. We document herein a case of poroid hidradenoma studied by immunoperoxidase techniques. Our immunohistochemical results are similar to those of other poroid neoplasms. These also support the inclusion of this tumor as the fourth variant within the eccrine poroma group of tumors.