Gene expression profiling guiding diagnosis and therapy of rare mammary-like anogenital gland carcinomas.

Cancers derived from anogenital mammary-like glands are rare, and their identification and selection of treatment for dissemination may be difficult. We encountered two such tumors, which both presented as occult primaries with nodal and hematogenous metastases. They were studied by immunohistochemistry, HER2 receptor assay, and gene expression profiling. Both tumors had some microscopical and immunohistochemical features in common with breast cancer, but lacked estrogen and progesterone receptors. Taxane-platinum-based systemic chemotherapy did not stop progression in a male patient, in whom a developing inguinal skin lesion was the likely primary tumor. The same regimen gave partial remission in a later, female, patient. After the mammary-like, HER2 positive nature of her tumor was confirmed by gene expression profiling using CupPrint and TargetPrint assays, treatment with vinorelbine-trastuzumab induced complete remission that is maintained by trastuzumab alone for almost 4 years after initial diagnosis. Molecular and immunohistochemical characterization of these rare tumors may identify them and sometimes guide systemic chemotherapy away from a non-specific and "broad spectrum" regimen toward a targeted therapy, resulting in greater effectiveness with less side effects.