Neoplasms of sweat glands and the breast may be morphologically and immunophenotypically similar. A recent study showed that TRPS1 staining is a highly sensitive and specific marker for
breast carcinoma. In this study, we analyzed TRPS1 expression in a spectrum of cutaneous sweat gland
tumors. We stained five microcystic adnexal
carcinomas (MACs), three eccrine
adenocarcinomas, two syringoid eccrine
carcinomas, four hidradenocarcinomas, six porocarcinomas, one eccrine
carcinoma-NOS, 11
hidradenomas, nine
poromas, seven
cylindromas, three
spiradenomas, and 10
syringomas with TRPS1
antibodies. All of the MACs and
syringomas were negative. Every
cylindroma and two of the three
spiradenomas demonstrated intense staining in cells lining the ductular spaces, with negative to relatively weak expression in surrounding cells. Of the 16 remaining malignant entities, 13 were intermediate to high positive, one was low positive, and two were negative. From the 20
hidradenomas and
poromas, intermediate to high positivity was revealed in 14 cases, low positivity in three cases, and negative staining in three cases. Our study demonstrates a very high (86%) expression of TRPS1 in malignant and benign adnexal
tumors that are mainly composed of islands or nodules with polygonal cells, e.g.,
hidradenomas. On the other hand,
tumors with small ducts or strands of cells, such as MACs, appear to be completely negative. This differential staining among types of sweat gland
tumors may represent either differential cells of origin or divergent differentiation and has the potential to be used as a diagnostic tool in the future.