# A Rare Case of Primary Intraosseous Mucoepidermoid Carcinoma of the Maxilla Diagnosed by MAML2 FISH Testing After Initial Misdiagnosis

## TL;DR

A rare case of maxilla cancer was correctly diagnosed using MAML2 FISH testing after an initial misdiagnosis.

## Contribution

Demonstrates the diagnostic utility of MAML2 FISH testing for intraosseous mucoepidermoid carcinoma.

## Key findings

- Primary intraosseous mucoepidermoid carcinoma is exceedingly rare, with only nine documented cases.
- MAML2 FISH testing confirmed the diagnosis after initial misdiagnosis as a benign tumor.
- Retrospective analysis showed the same diagnosis could have been made earlier.

## Abstract

We report a case of primary intraosseous mucoepidermoid carcinoma of the maxilla, an exceedingly rare condition with only nine cases documented in the literature, contributing to a prolonged diagnostic timeline. A 58-year-old woman underwent surgery four years earlier for a left maxillary mass at another hospital, initially diagnosed as a calcifying epithelial odontogenic tumor. Due to residual tumor growth, she was referred to our hospital for a second surgery. Histopathological analysis and MAML2 gene fluorescence in situ hybridization (FISH) testing confirmed the diagnosis of mucoepidermoid carcinoma. A retrospective review of the tissue from the initial surgery revealed the same diagnosis. This disease poses diagnostic challenges as imaging and histological findings often resemble benign odontogenic cysts. Accurate diagnosis requires awareness of this condition and the application of definitive diagnostic tools. This case highlights the importance of considering intraosseous mucoepidermoid carcinoma in the differential diagnosis of jawbone lesions and the diagnostic utility of MAML2 FISH testing.