The clinical outcome, pathologic spectrum, and genomic landscape for 454 cases of salivary mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary tumor. A complete understanding of the high heterogeneity of MEC in histology and genetics would help in accurate diagnosis and treatment. Therefore, We evaluated the clinical features, treatment outcomes, and pathological parameters of 454 MECs and analyzed their genomic features using whole-exome sequencing and whole-transcriptome sequencing. We found that MECs predominantly occurred in females and those in their 4th-5th decades. The parotid gland was the most frequently affected site. All patients underwent complete mass resection with lobectomy; 414 patients were alive without relapse at follow-up, after an average period of 62 months (1-116 months). The disease progressed after initial treatment in 40 patients. The lungs were the most common site of distant metastasis. For classical MECs, histologic gradings of the AFIP, modified Healey, and MSK systems were significantly associated with recurrence and lymph nodal metastasis; these gradings were significantly related to lymph nodal metastasis for the subtypes. Older age, minor salivary gland involvement, clinical symptoms, high TNM stage, high-grade tumor, and improper surgical modality were the main prognostic factors. BAP1 was the most frequently mutated gene in MEC. Mutations in CDKN2A, MET, and TP53 were more frequently found in aggressive tumor phenotypes. MAML2 rearrangement was observed in 42% of patients, and EWSR1 rearrangement in 8%. Specific genetic events (in TP53 and FBXW7) with CRTC1::MAML2 fusion superimposed might be associated with unfavorable prognosis. This study provides new insights into precision therapeutic strategies for MEC.