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Comparative Lesions Analysis Through a Targeted Sequencing Approach

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Novel Histologic Features in Ameloblastoma With RASQ61R Mutation.

Ivan J Stojanov¹, Anna M Trzcinska^2,3, Mohammed Qaisi^4,5

¹Department of Pathology and Laboratory Medicine, Cleveland Clinic.

The American Journal of Surgical Pathology

|February 19, 2025

Summary

This summary is machine-generated.

Ameloblastoma can exhibit unusual histological features and lack typical differentiation markers. Molecular testing, particularly for RAS mutations, is crucial for diagnosing these challenging ameloblastoma cases.

Keywords:

BRAF HRAS MAPK NRAS ameloblastic carcinoma ameloblastoma odontogenic tumor

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Area of Science:

Oral Pathology
Molecular Oncology
Head and Neck Neoplasms

Background:

Ameloblastoma typically shows ameloblastic differentiation and MAPK pathway alterations, including BRAFV600E and RAS mutations.
These molecular profiles are consistent across known histological variants, even those with subtle differentiation.

Purpose of the Study:

To describe four cases of maxillary ameloblastoma with atypical histological features not aligning with established variants.
To highlight the importance of molecular diagnostics in identifying ameloblastoma when histological evidence is ambiguous.

Main Methods:

Histopathological examination of four maxillary ameloblastoma cases with unusual features.
Molecular analysis, including mutation-specific immunohistochemistry for RAS Q61R mutations.

Main Results:

Three intraosseous tumors showed spindled to basaloid cells with varied growth patterns and NRASQ61R mutations, despite minimal or absent ameloblastic differentiation.
A fourth peripheral case with squamoid morphology harbored HRASQ61R mutation, with positive staining supporting surface origin.

Conclusions:

Ameloblastoma can present with non-traditional histology, sometimes lacking overt ameloblastic differentiation, broadening the differential diagnosis.
Accurate diagnosis of these atypical ameloblastomas requires a high index of suspicion and confirmation via molecular testing or mutation-specific immunohistochemistry.