Barnaculate Carcinoma - A new terminology for the recognition of a histologically familiar entity.

Abstract

Proliferative Verrucous Leukoplakic (PVL) is a recently recognized Oral Potentially Malignant Disorder (OPMD) with the highest malignant transformation potential. These lesions are often resistant to the treatment and present with varied clinical and histological pictures in their course of progression. The histological spectrum observed in PVL are often confusing attributable to the extensive verrucous surface proliferation rendering an improper histological diagnosis, thus compromising treatment. To address the diagnostic ambiguity within this spectrum, Thompson et al. (2021) proposed four histopathologic categories for PVL, introducing the novel entity Barnaculate Carcinoma (BC). BC occupies an intermediate stage between Verrucous Hyperplasia (VH) and Verrucous Carcinoma (VC) and is defined as a bulky, non-invasive epithelial proliferation with distinctive morphological features, including extensive endophytic growth, flat surface, and an intact basement membrane. It resembles VC but lacks the classic invasion or extension beyond the adjacent epithelium. The name draws from barnacles, which attach firmly to surfaces-a trait mirrored in the lesion's 'stuck-on' appearance. While BC has not been recognized in the latest WHO 2022 classification of Head and Neck Tumours, it represents a unique subset specific to PVL, with no reported nodal metastasis or mortality in a limited follow-up. The delineation of BC could refine diagnosis and treatment, distinguishing it from VH and VC. However, further studies are warranted to validate its biological behaviour and determine therapeutic protocols. Recognizing BC in biopsies and evaluating patient outcomes will be critical in shaping future classification and management strategies.