The reliability of MAML2 gene rearrangement in discriminating between histologically similar glandular odontogenic cysts and intraosseous mucoepidermoid carcinomas

Objective: MAML2 expression is proven in the majority of mucoepidermoid carcinomas (MECs) arising in salivary glands. MEC can also occur intraosseously (IMEC). Glandular odontogenic cyst (GOC) is an odontogenic cyst with histologic overlap with IMEC. This study aimed to determine the reliability of MAML2 in distinguishing IMEC cases from GOC cases. Study Design: An institutional review board–approved retrospective search of IMEC, GOC, and IMEC with prior history of GOC was performed within the archives of the University of Florida and the University of Alberta Oral Pathology Biopsy Services. Nine cases from 5 patients were selected. Break-apart fluorescent in situ hybridization analysis was performed on 7 cases for the presence of MAML2 rearrangement. Results: Four cases had negative MAML2 gene rearrangement, and 3 cases had positive MAML2 gene rearrangement. Conclusions: Although it can be concluded that the 3 cases with positive translocation for MAML2 were IMECs, the same conclusion could not be drawn for the 4 cases with negative translocation. Whether the cases that were negative for translocation were GOCs with MEC-like islands or were MAML2-negative IMECs could not be ascertained. Therefore, MAML2 rearrangement is not always reliable in differentiating IMECs from GOCs with overlapping histology.