Characterization of the epithelial components in pleomorphic adenoma of the salivary gland

OBJECTIVE: To clarify the cytomorphologic characteristics of luminal epithelial cells (LEC) and neoplastic myoepithelial cells (NMC) in pleomorphic adenoma (PA). STUDY DESIGN: Imprint cytologic smears stained with Papanicolaou stain were examined in 20 patients with PA (including recurrent cases). Immunocytochemistry was performed using the antibodies of epithelial membrane antigen (EMA) and carcinoembryonic antigen (CEA); cells positive for both CEA and EMA were interpreted as LEC and those negative as NMC. RESULTS: LEC were found in 9 of 20 cases as cell clusters in various shapes or as isolated cells with ample cytoplasm. NMC were classified into four types according to their visual patterns and cytoplasmic features: type A, isolated cells with ample cytoplasm; type B, isolated naked cells; type C, cluster of cells with ample cytoplasm; and type D, cluster of cells with scant cytoplasm. NMC were found in all 20 cases, with an absolute incidence of 100%, 90%, 65% and 50%, respectively. CONCLUSION: The different features of NMC (Types A-D) are essential to a specific differential diagnosis. This classification was useful to discriminate PA from other salivary gland tumors with NMC.