Challenges in the Diagnosis of Myoepithelial-Rich Salivary Gland Neoplasms

Salivary gland neoplasms are both rare and strikingly heterogeneous in their morphology, a combination that may result in vexingly broad differential diagnoses. This is particularly true of myoepithelial-rich tumors, as neoplastic myoepithelial cells can assume a multiplicity of phenotypes, and associated epithelial cells may be present to varying degrees. An accurate diagnosis requires a thorough familiarity with characteristic morphology and conversance with appropriate ancillary studies. Here, we review 4 myoepithelial-rich tumors (myoepithelioma, myoepithelial carcinoma, myoepithelial-rich pleomorphic adenoma, and epithelial-myoepithelial carcinoma), comparing and contrasting their characteristic morphology, immunohistochemical profiles, and cytogenetic/molecular features, with an emphasis on accurate and efficient narrowing of the differential diagnosis.