Plexiform ameloblastoma: a potential diagnostic challenge.

Objective: Ameloblastoma is a benign, locally aggressive neoplasm of the jaws. Accurate diagnosis is important for providing timely treatment and reducing the risk of recurrence and local destruction. The criteria for diagnosing ameloblastoma are well-defined, however, rare cases have been observed with a multicystic/unicystic plexiform pattern that lacks pathognomonic histologic features, causing difficulties in differentiating them from less aggressive jaw lesions. Our main objective was to review these plexiform ameloblastomas that could prove challenging for pathologists on incisional biopsies.

Study design: We reviewed cases of ameloblastoma in the University of Toronto diagnostic biopsy service from 2004 to 2024, n = 200. Cases with a microscopic description of cystic plexiform epithelial proliferation were retrieved for analysis of histopathologic features, clinical and radiographic information.

Results: A rare subset of ameloblastoma (4%, 8 of 200) presented a distinctive histologic appearance of cystic plexiform proliferation lacking ameloblast-like cells, but clinical and radiographic features characteristic of ameloblastoma. Immunohistochemical staining for the BRAF p.V600E mutation was positive in 7 of 8 cases, demonstrating the importance of BRAF testing to aid in diagnosis.

Conclusions: Our study highlights an uncommon and potentially challenging histologic pattern of ameloblastoma for which a coordinated approach using clinical, radiographic, histologic, and molecular studies are needed for timely and accurate diagnosis.