Salivary gland mucoepidermoid carcinoma is a clinically, morphologically and genetically heterogeneous entity: a clinicopathological study of 40 cases with emphasis on grading, histological variants and presence of the t(11;19) translocation

Aims: To correlate World Health Organization (WHO) grade, patient's outcome and presence of t(11;19) to histological tumour variants in 40 well-characterized mucoepidermoid carcinomas (MECs). Methods and results: MECs were classified as 'classical' based on the presence of equal proportions of the three cell types or the dominance (>= 50%) of mucous cells together with at least one other cell type, and as 'variant' if composed of >= 80% of a single non-mucous cell type. Classical MECs were more common (n = 23). Variant MECs had predominant squamoid (n = 9), eosinophilic (n = 5) or clear cell (n = 3) morphology. Twenty-seven tumours were WHO grade 1, three grade 2 and ten grade 3. The t(11;19) was detected in 82%, 35% and 0% of classical MEC, variant MEC and non-MEC, respectively. Classical MECs were associated significantly with age < 60 years (P < 0.001), grade 1 (P < 0.001) and t(11;19) (P = 0.003). Short overall survival was associated significantly with age > 60 years (P = 0.001) and Union for International Cancer Control (UICC) stage > I (P = 0.031), residual tumour (P < 0.001), tumour grade > 1 (P = 0.001) and squamoid variant (P = 0.002) in Kaplan-Meier analysis. Conclusions: The results underscore the great histological diversity of MEC, the reproducibility of the WHO grading criteria and the value of histological subtypes as an additional prognostic factor.