TRPS1 Reliably Stains Benign and Malignant Lesions Arising Within Vulvar Anogenital Mammary-like Glands.

TRPS1 is a novel immunohistochemical marker that is known to stain normal mammary epithelium and breast carcinomas (especially triple negative carcinomas). TRPS1 staining has also been reported in normal skin appendages, benign and malignant cutaneous neoplasms, and anogenital mammary-like glands (AGMLG). However, research regarding TRPS1 staining in various neoplasms derived from AGMLG is limited. Past studies have focused on two neoplasms of AGMLG-hidradenoma papilliferum (HP) and extramammary Paget disease (EMPD). We confirm the finding that TRPS1 is positive in the epithelium of HP and we report its expression in a variety of other benign and malignant lesions derived from vulvar AGMLG, including fibroepithelial lesion (FEL), lactating adenoma (LA), fibroepithelial polyp with AGMLG, and mammary-type adenocarcinoma (MAc). The majority of TRPS1 staining was diffuse and displayed strong (3+) intensity. We show that TRPS1 is significantly more sensitive than GCDFP-15 in lesions of AGMLG and is comparable to GATA3. TRPS1 was also more sensitive than mammaglobin, but the finding did not reach statistical significance. TRPS1 demonstrated diffuse staining in these lesions significantly more often than either GCDFP-15 or mammaglobin. This study was limited by its small sample size, due to the rarity of some entities such as the malignant MAc (n=3).