Glandular Odontogenic Cysts (GOCs) Lack MAML2 Rearrangements: A Finding to Discredit the Putative Nature of GOC as a Precursor to Central Mucoepidermoid Carcinoma

Abstract

Glandular odontogenic cyst (GOC) is a cyst of the gnathic bones that is characterized by squamous and glandular differentiation. The histopathologic features of GOC overlap considerably with central mucoepidermoid carcinoma (MEC), suggesting that GOC could be a precursor lesion to, or even a low-grade form of, central MEC. Differentiating the two lesions may be difficult or impossible on a limited biopsy. MAML2 rearrangements have been recently found to be specific for MEC, even those arising in the jaws. An analysis of MAML2 in GOCs could help clarify its relationship with central MEC. Tissue blocks from 21 GOCs and 5 central MECs were retrieved from the surgical pathology archives of The Johns Hopkins Hospital. Each MEC exhibited solid areas and clear-cut stromal invasion. In addition, 4 of the MECs demonstrated cystic areas that were histologically similar to GOC. Break-apart fluorescence in situ hybridization for MAML2 was performed. For the MECs, analysis was performed on both the solid components and the cystic areas that resembled GOC. MAML2 rearrangements were identified in all 5 of the MECs, but in none of the 21 GOCs (100 vs. 0%; p<0.0001, Fisher's Exact). In the MECs, the rearrangement was present in both the solid and GOC-like cystic areas. While central MECs consistently harbor the MAML2 rearrangement, even in low-grade cystic areas that resemble a pre-existing GOC, true GOCs do not. Accordingly, GOC does not appear to represent an early or low-grade form of central MEC, but rather an unrelated lesion. The high sensitivity and specificity of MAML2 rearrangement for MECs points to its utility as a diagnostic adjunct in separating mucinous cystic lesions of the gnathic bones.