Clinicopathological significance of EGFR pathway gene mutations and CRTC1/3-MAML2 fusions in salivary gland mucoepidermoid carcinoma.

AIMS: Mucoepidermoid carcinoma (MEC) is one of the most common salivary gland carcinomas. Epidermal growth factor receptor (EGFR) signalling pathway gene mutations are important in predicting a patient's prognosis, selecting molecularly targeted drugs and estimating the efficacy of a molecular therapy. However, their significance in MEC have been poorly clarified. CRTC1/3-MAML2 fusions are specific to MEC and may be associated with favourable characteristics in these patients. METHODS AND RESULTS: We looked for CRTC1/3-MAML2 fusions and gene alterations in the EGFR, RAS family (KRAS, HRAS and NRAS), PIK3CA, BRAF and AKT1 in 101 MEC cases. We also examined mutations in TP53. CRTC1/3-MAML2 fusions were found in 62.4% of the cases. KRAS, HRAS and PIK3CA mutations were detected in 6.9%, 2.0% and 6.9%, respectively, but other EGFR pathway genes were not mutated. In total, gene mutations (RAS/PIK3CA) in the EGFR pathway were detected in 14.9% of the cases. TP53 mutations were found in 20.8%. CRTC1/3-MAML2 fusions were associated with a better prognosis and RAS/PIK3CA mutations a worse prognosis of the patients, respectively, and both were selected as independent prognostic factors for the overall survival of the patients. TP53 mutations had no prognostic impact. CRTC1/3-MAML2 fusion-positive rates were inversely associated with the patients' age and the fusions were found in 82% of patients aged < 30 years. CONCLUSIONS: RAS/PIK3CA mutations were frequently detected, and may be a biomarker for a poorer prognosis in MEC patients. CTRC1/3-MAML2 fusions were positive in most of the young MEC patients.