Atypical Squamous Verrucous Lesions of the Oral Cavity: Challenges in Interpretation of Small Incisional Biopsies

Squamous verrucous proliferative lesions of oral cavity can pose a diagnostic challenge for the general pathologist, especially on small biopsies. The superficial nature of incisional biopsies and inconsistent histologic terminologies used for these lesions contribute to often-discrepant clinical diagnosis, resulting in delayed treatment. This study aims to explore the proliferative squamous lesions of oral cavity, correlate biopsy & resection diagnoses, and evaluate possible reasons for discrepant diagnosis (if any).

A retrospective review of oral verrucous squamous lesions was undertaken. Pathology database was searched for oral cavity biopsies from January2018 through August2022 with the keywords: atypical, verrucous, squamous, and proliferative. Cases with follow-up were included in this study. A blinded review of the biopsy slides was performed and documented by a single head and neck pathologist. Demographic data, biopsy and final diagnosis were recorded.

Twenty-three cases met criteria for inclusion. The mean patient age was 61.1 years with a male: female ratio of 1.09. Most frequent site was lateral border of tongue (36%) followed by buccal mucosa and retromolar trigone. The most common biopsy diagnosis was "Atypical squamoproliferative lesion, excision recommended" (n = 16/23, 69%) with 13/16 showing conventional squamous cell carcinoma (SCC) on follow-up resection. 2/16 atypical cases underwent repeat biopsy for confirmation of diagnosis. Overall, conventional SCC was the most prevalent final diagnosis (73%, n = 17), followed by verrucous carcinoma (17%, n = 4). On slide review, six initial biopsies were reclassified as SCC, while one final diagnosis was reclassified as a hybrid carcinoma (on resection specimen). Diagnostic concordance (biopsy and resection) was observed in three cases, all three were recurrences. The primary reasons for discrepant diagnosis on initial biopsies were found to be 1. Obscuring inflammation, 2. Superficial biopsies, and 3. Under recognition of morphologic features (e.g., tear shaped rete, loss of polarity, dyskeratotic cells, paradoxical maturation) that help differentiate dysplasia from reactive atypia.

This study highlights the rampant interobserver variability in diagnosis of oral cavity squamous lesions and emphasizes importance of identifying morphologic clues that can aid in correct diagnosis, thereby helping in adequate clinical management.