TRPS1 Is Consistently Expressed in Hidradenoma Papilliferum.

TRPS1 is a novel immunohistochemical marker, so far quite specific and sensitive for breast cancer and especially useful for the diagnosis of triple-negative breast cancer. TRPS1 expression has recently been reported in normal skin appendages, as well as in a variety of benign and malignant cutaneous tumors, including adnexal tumors. However, it has not yet been reported in hidradenoma papilliferum (papillary hidradenoma), a benign adnexal neoplasm, accepted to originate from mammary-like glands in the vulvar or anogenital region of middle-aged women. We report consistent nuclear expression of TRPS1 in the epithelium of 9/9 cases of hidradenoma papilliferum, while in 2/2 cases with foci of oxyphilic metaplasia, these foci were consistently negative for TRPS1 immunohistochemistry. Our findings are in line with the theory that hidradenoma papilliferum is derived from mammary-like glands and showed that TRPS1 can be an additional sensitive immunohistochemical marker for hidradenoma papilliferum.