Morphologic Feature Guiding Discovery of Driver Genetic Alteration in Rare Entity

Adenoid Ameloblastoma is a very rare benign odontogenic tumor characterized microscopically by epithelium resembling conventional ameloblastoma, with additional duct-like structures, epithelial whorls, and cribriform architecture. Dentinoid deposits, clusters of clear cells, and ghost-cell keratinization may also be present.These tumors do not harbor BRAF or KRAS mutations and their molecular basis appears distinct from conventional ameloblastoma but remains unknown. Dr. Carolina Cavalieri Gomes from the Universidade Federal de Minas Gerais in Brazil, discusses her team’s discovery of CTNNB1 (beta-catenin) exon 3 mutations in 4 of 9 primary cases and 2 additional recurrences.

While the occasional presence of ghost cells keratinization was the feature that led the team to initially investigate beta-catinin, this feature was present in only 2/6. Furthermore, nuclear beta-catenin immunoexpression (IHC) was found in 7 of 8 tested samples including some with wild type CTNNB1. The findings support the classification of adenoid ameloblastoma as a separate entity, and not as a subtype of ameloblastoma. The use of beta-catenin IHC could help in establishing the diagnosis in challenging cases.