A reappraisal of the MECT1/MAML2 translocation in salivary mucoepidermoid carcinomas

• Published in: The American journal of surgical pathology Vol. 34; no. 8; p. 1106
• Main Authors: Seethala, Raja R, Dacic, Sanja, Cieply, Kathleen, Kelly, Lindsey M, Nikiforova, Marina N
• Format: Journal Article
• Language: English
• Published: United States 01.08.2010
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Carcinoma, Mucoepidermoid - genetics; Carcinoma, Mucoepidermoid - mortality; Carcinoma, Mucoepidermoid - pathology; Chi-Square Distribution; Child; Disease-Free Survival; Female; Gene Expression Regulation, Neoplastic; Humans; In Situ Hybridization, Fluorescence; Kaplan-Meier Estimate; Male; Middle Aged; Neoplasm Staging; Oncogene Proteins, Fusion - genetics; Prognosis; Retrospective Studies; Reverse Transcriptase Polymerase Chain Reaction; Salivary Gland Neoplasms - genetics; Salivary Gland Neoplasms - mortality; Salivary Gland Neoplasms - pathology; Time Factors; Translocation, Genetic; Young Adult
• ISSN: 1532-0979
• DOI: 10.1097/PAS.0b013e3181de3021

The MECT1/MAML2 translocation is identified in a large proportion of mucoepidermoid carcinomas (MEC) of the salivary gland and is an emerging favorable prognosticator. However, there are conflicting data on this translocation's specificity, restriction to low/intermediate MEC, and strength as a prognosticator. We present our experience with the MECT1/MAML2 translocation in a large cohort of MECs to address these issues. We analyzed 55 salivary MEC and 36 potential MEC mimics (24 Warthin tumors, 5 oncocytomas, 3 squamous cell carcinomas, 2 squamoid salivary duct carcinomas, 1 lymphoepithelial cyst, 1 Schneiderian carcinoma ex papilloma) for presence of the MECT1/MAML2 translocation by fluorescent in-situ hybridization (FISH) and real-time RT-PCR. Overall, MECT1/MAML2 translocation was present in 36/55 (66%) of MEC whereas all 36 non-MEC were negative for translocation. Low or intermediate-grade MEC had a higher frequency of translocation (75%) than high-grade MEC (46%) (P=0.039). Translocation positive cases had a better disease-specific survival (log rank P=0.026) although 2 patients still died of disease. Within high-grade MEC, MECT1/MAML2 positive tumors had lower rates of anaplasia (P=0.001), and mitotic counts (P=0.012). Thus, MECT1/MAML2 translocation is highly specific for MEC and imparts a better prognosis. However, it is frequent even within high-grade MEC and can be seen in lethal cases suggesting that translocation status should not supersede conventional parameters. There are 2 distinct subgroups within high-grade MEC, and the translocation negative tumors may actually be more appropriately categorized as another tumor type (such as adenosquamous carcinoma).