Cytopathological features of an epithelial-myoepithelial carcinoma with predominant clear myoepithelial cells in the parotid gland.

Epithelial-myoepithelial carcinoma (EMC) is a rare low-grade carcinoma occurring most frequently in the parotid gland. Most EMCs consist of two cell types that typically form double-layered ductal structures. However, occasionally EMC presents predominantly clear myoepithelial cells. A 34-year-old man visited in August 1993 and was diagnosed as having clear-cell carcinoma. The tumor was curatively resected. However, in the following 5 years, recurrence developed a total of five times. The imprint cytological feature of the recurrence at the third time showed monophasic clear cells in sheet clusters with overlapping. Most of the clear tumor cells presented an expression to alpha-smooth muscle actin (SMA). The imprint cytological feature of the recurrence at the fifth time showed increase of nuclear atypia with coarse chromatin patterns and large nucleoli. In addition to cytological findings, the cytological diagnosis of EMC with predominant clear myoepithelial cells requires a definite expression to SMA.