An immunohistochemical panel for reliable differentiation of salivary duct carcinoma and mucoepidermoid carcinoma.

Salivary duct carcinoma is a highly aggressive salivary gland malignancy that may be misdiagnosed as high-grade mucoepidermoid carcinoma. We utilized tissue microarrays with 78 examples of mucoepidermoid carcinoma and 47 salivary duct carcinomas to evaluate the utility of an immunohistochemical panel consisting of androgen receptor, Her2/neu, p63, and cytokeratin 5/6 in distinguishing these entities. Among all cases in the cohorts, androgen receptor was highly specific for salivary duct carcinoma, while cytokeratin 5/6 and p63 were specific for mucoepidermoid carcinoma. While the rate of unequivocal Her2/neu overexpression among the salivary duct carcinomas was low (8.9 %), discrimination of salivary duct carcinoma was enhanced when this marker was used in combination with androgen receptor due to profound sensitivity. The immunohistochemical panel was particularly efficacious at distinguishing the problematic subset of high-grade mucoepidermoid carcinomas from salivary duct carcinoma. Utilization of this set of immunohistochemical markers allows reliable differentiation of salivary duct and mucoepidermoid carcinoma, a distinction with important prognostic and therapeutic implications.