Clinicopathologic and molecular features of myoepithelial tumors of salivary glands

Objective To investigate the clinicopathological, and molecular characteristics of myoepithelial tumors (MTs) of salivary glands. Methods A total of 37 MTs cases including 13 malignant epithelial tumors (MMTs) and 24 benign epithelial tumors (BMTs) of salivary glands were identified from the archives of the Department of Pathology, General Hospital of Eastern Theater Command, dating from 2006 to 2016. Clinical features, histological patterns, immunohistochemical characteristics and status of EWSR1 gene rearrangement by fluorescence in situ hybridization (FISH) analysis were reviewed in all cases. Results Clinically, 37 MTs cases mainly occurred in the parotid glands, when most of the patients presented with painless masses. Of the 13 MMTs cases, male to female ratio was 7∶6, and the median age was 62 years old. Of the 24 BMTs cases, male to female ratio was 5∶7, and the median age was 54 years old. Immunohistochemically, 37 MTs cases were positive for CKpan, and at least one myoepithelial marker. Twenty six of 37 MTs cases were analyzable for the EWSR1 gene break by FISH. Based on the previous evaluation criterion, the EWSR1 translocation was detected in 4 cases of 11 MMTs, and 4 cases of 15 BMTs. According to the main histological composition of tumor cells, 4 EWSR1-positive MMTs covered 2 clear-cell cases and 2 epithelioid-cell cases, when 4 EWSR1-positive BMTs covered 2 clear-cell cases, 1 plasmacytoid-cell case, and 1 spindle-cell case. Conclusions Males and females are affected equally. MTs express immunoreactivity for CKpan, and at least one myoepithelial marker. The EWSR1 rearrangement is present in a subset of MTs, with variable morphological characteristics, and has no statistical significance on clinical behavior. Key words: Salivary gland neoplasms; Myoepithelioma; Immunohistochemistry