Adenoid Ameloblastoma Shares Clinicopathologic, Immunohistochemical, and Molecular Features With Dentinogenic Ghost Cell Tumor

Abstract

The updated classification of odontogenic tumors by the World Health Organization (WHO) has included adenoid ameloblastoma (AA) as a distinct entity. However, distinguishing between AA and dentinogenic ghost cell tumor (DGCT) can still be challenging due to their significant morphologic similarities. In this study, we aimed to compare the clinicopathologic, immunohistochemical, and molecular characteristics of AA and DGCT to aid in their differentiation and to shed light on their pathologic mechanisms. Thirteen cases of AA and 14 cases of DGCT (15 samples) were analyzed, along with 11 cases of adenomatoid odontogenic tumor (AOT) and 18 cases of conventional ameloblastoma (AM) for comparative purposes. The study found that AA and DGCT shared a similar long-term prognosis. Immunohistochemically, all cytokeratins detected, except CK8/18, were not statistically significant in differentiating AA and DGCT, while there was a statistically significant difference in the immunophenotype of CK7 and CK10/13 between AA and AM. Nuclear β-catenin accumulation were detected in all cases of AA and DGCT, while AOTs and AMs exhibited cytoplasmic β-catenin. Molecularly, CTNNB1 hotspot mutations were found in only 1 case of AA (1/13), but not found in the other 3 types of tumors. BRAF p.V600E mutation was positive in 2/13 (15%) AA, 1/15 (7%) DGCT, and 2/11 (18%) AOT cases. In comparison, conventional AM was positive for BRAF p.V600E mutation in 94% (17/18) of cases, while KRAS mutations were detected in 63% (7/11) of AOT cases. The study suggests that the so-called AA is a rare benign tumor that exhibits clinical, immunohistochemical, and molecular features similar to DGCTs. Based on these findings, AA should not be categorized as a standalone entity solely based on the presence of whorls/morules and cribriform/duct-like structures. Further studies are needed to investigate the pathologic mechanisms of these tumors and to identify potential therapeutic targets.