Salivary duct carcinoma. Part II. Immunohistochemical evaluation of 13 cases for estrogen and progesterone receptors, cathepsin D, and c-erbB-2 protein.

Salivary duct carcinoma is an infrequent highly aggressive salivary gland tumor that is histologically similar to ductal carcinoma of the breast. We studied 13 cases by immunohistochemistry for the presence of estrogen and progesterone receptors, cathepsin D, and c-erbB-2 protein to determine whether the similarity to breast carcinoma extended beyond the light microscope to the molecular level and, if so, whether these markers might have therapeutic or prognostic value. Twelve of 13 cases contained sufficient amounts of tumor tissue for evaluation. Of these 12 cases, one (8%) was positive for estrogen receptors, none was positive for progesterone receptors, five (42%) were positive for cathepsin D, and three (25%) were positive for c-erbB-2 protein. Expression of cathepsin D and c-erbB-2 protein does not appear to have prognostic significance in salivary duct carcinoma. The 8% incidence of immunopositivity for estrogen receptors and absence of progesterone receptors in salivary duct carcinoma is considerably less than that seen in breast cancer. Nevertheless, because the occurrence of systemic metastasis in salivary duct carcinoma is such an ominous development largely unresponsive to chemotherapy, antihormonal therapy, such as used in breast cancer, might be considered on a trial basis for those tumors that are estrogen receptor-positive when conventional therapeutic modalities fail.