Immunohistochemical and Molecular Characteristics of Anogenital Papillary Hidradenomas.

ABSTRACT

BACKGROUND: Papillary hidradenomas (PHs) of the anogenital region are uncommon tumors whose immunohistochemical and molecular profile have been infrequently studied. MATERIAL AND METHODS: We studied 15 PHs by next-generation sequencing and 10 immunohistochemical markers (PAX8, GATA3, HER2, MSH6, PMS2, estrogen, progesterone and androgen receptors, CK14, and NKX3.1). RESULTS: All cases expressed GATA3, whereas none expressed PAX8, and rare tumor cells were NKX3.1-positive. Almost all cases expressed estrogen receptors (ER), progesteron receptors (PR), and androgen receptors (AR). CK14 was expressed by myoepithelial cells, whereas only rarely by the epithelial tumor cells. HER2 showed no significant expression. Immunohistochemical expression for the mismatch repair proteins showed persistence in all cases. Molecular analysis often showed PIK3CA mutations, as well as KRAS , SMO , and MAP2K1 mutations. CONCLUSION: Anogenital PHs frequently harbor PIK3CA mutations and show a PAX8-, GATA3/ER/PR/AR + immunohistochemical profile.