MOLECULAR DETECTION OF MECT1-MAML2 FUSION GENE IN MUCOEPIDERMOID CARCINOMA WITH ORDINARY AND VARIANT HISTOLOGY: A STUDY USING ARCHIVAL PARAFFIN EMBEDDED TISSUE

Abstract

Mucoepidermoid carcinoma (MEC) has been characterized by t (11; 19)(q21; p13). This chromosomal translocation has been recently shown to generate a MECT1- MAML2 fusion gene. MEC can pose diagnostic challenges when they are of high-grade, of variant histologic appearance and occurring in an unusual site. The aim of this study was to evaluate the frequency of the MECT1-MAML2 fusion gene among primary salivary gland MECs and extrasalivary gland MECs, together with some histological variants and its role as a possible diagnostic adjunct, comparing the salivary gland tumors including Warthin's tumor(WT)，pleomorphic adenoma(PA)，and adenoid cystic carcinoma(ACC). Using a reverse transcription-polymerase chain (RT-PCR)-based approach, we assayed for the MECT1-MAML2 transcript in 39 cases for which paraffin- embedded tumor tissue with adequate RNA was available. These included 19 MECs，10 WTs， five PAs， and five ACCs. The MECT1-MAML2 fusion gene transcript was detected in 16 (84.2%) of 19 MECs. These positive cases included two cases of MEC with WT-like areas，a sclerosing MEC and a clear cell MEC. Three negative cases were high- grade MECs. Two of them were not easy to distinguish from squamous cell carcinoma. The MECT1-MAML2 fusion gene was negative in all cases of WT，PA and ACC. The potential usefulness of MECT1-MAML2 fusion gene expression as a molecular marker in the diagnosis of MEC is supported.