Breast cancers metastasizes to the skin relatively often, where they problematically mimic primary cutaneous neoplasms both morphologically and immunohistochemically. Authors identified 12 cutaneous breast carcinoma metastases (including 11 ductal and one basal type carcinoma ) and 11 sweat gland carcinomas (including 5 eccrine, 3 microcystic and 3 porocarcinomas) which they immunohistochemically stained for mammaglobin, gross cystic disease fluid protein 15 (GCDFP-15), p63, basal cytokeratins CK5, CK14, and CK17, androgen receptor, and PAX5 protein expression.
A simple scoring system based on tumor staining for 5 antigens: mammaglobin, p63, CK5, CK14, and CK17 was created based on the predicted metastatic breast cancer phenotype, mammaglobin+, p63-, CK5-, CK14-, CK17-. Single points were awarded for each discrepant phenotype, and scores of > 3 were used to identify sweat gland carcinomas. By numerical scoring, this five stain immunopanel was 100% sensitive and 91% specific in distinguishing sweat gland carcinomas from cutaneous breast cancer metastases. Tumor staining for 5 antigens: mammaglobin, p63, CK5, CK14, and CK17 as a very highly sensitive and a highly specific discriminator of sweat gland carcinomas from cutaneous breast cancer metastases.
Separate investigators have applied podoplanin staining to a small number of sweat gland carcinomas ,which were podoplanin POSITIVE as opposed to metastatic breast cancers, which were podoplanin NEGATVE. In the future, podoplanin staining may be shown to also facilitate this problematic differential.
Marian Rollins-Raval et al. (2011) An Immunohistochemical Panel to Differentiate Metastatic Breast Carcinoma to Skin From Primary Sweat Gland Carcinomas With a Review of the Literature: Arch Pathol Lab Med. 135:975-983
Editorial. Guy E.Nichols MD, PhD.