Fluorescence in‐situ hybridization identifies Mastermind‐like 2 ( MAML2) rearrangement in odontogenic cysts with mucous prosoplasia: a pilot study

Aims The pathogenesis of intraosseous mucoepidermoid carcinoma ( IMEC ) remains unknown. Coexistence with odontogenic cysts ( ODC ) has been reported in 32–48% of IMEC . Furthermore, prosoplastic mucous cells are often seen in the epithelial lining of ODC s. MECT 1– MAML 2 fusion transcripts have been identified in >66% of salivary gland MEC cases. The aim of this study was to investigate the presence of MAML 2 rearrangement in ODC s featuring mucous prosoplasia. Methods and results Ten cases of ODC with a mucous cell component and three cases of IMEC were evaluated using fluorescence in‐situ hybridization. All cases occurred in the mandible. The ODC s exhibited a M:F ratio of 4:1 (mean age 49.2 years), while all IMEC s occurred in women (mean age 68.3 years). All three IMEC s demonstrated MAML 2 rearrangement, in 26–61% of tumour cells. Successful hybridization was observed in nine of 10 cases of ODC . In two of these nine, there was MAML 2 rearrangement in 12% and 24% of the lining epithelial cells, while three of the nine showed rearrangement in 7–8% of cells; the remaining four cases were negative. Conclusions We identified MAML 2 rearrangements in five of nine ODC s lined by mucus‐secreting cells. This suggests that at least a subset of ODC s with mucous prosoplasia are characterized by molecular events considered diagnostic for intraosseous and extraosseous MEC .