# Intraosseous Atypical Verrucopapillary Epithelial Proliferation with Verrucous Carcinoma Features Evolving from a Keratinizing Odontogenic Cyst: Report of an Uncommon Variant and Review of the Literature

## TL;DR

A rare case of a jawbone cyst evolving into a unique epithelial growth with features of verrucous carcinoma is reported and reviewed.

## Contribution

The paper presents an uncommon variant of intraosseous atypical verrucopapillary epithelial proliferation arising from a keratinizing odontogenic cyst.

## Key findings

- The lesion exhibited histopathologic features of verrucous carcinoma but lacked definite mural invasion.
- No recurrence was observed after 14 months of follow-up following surgical excision.
- Literature review suggests favorable prognosis for such lesions after complete excision.

## Abstract

Developmental odontogenic cysts (DOCs) of the jawbones with overt luminal keratinization, i.e., odontogenic keratocyst (OKC) and orthokeratinized odontogenic cyst (OOC), are relatively uncommon in head and neck/oral pathology practice. Notably, atypical verrucopapillary epithelial proliferations (AVPEP) arising from the epithelium of DOCs have rarely been reported and range from verrucous epithelial hyperplasia with or without cytologic dysplasia to verrucous carcinoma (VC). Published examples of intraosseous VC developing ex-DOC are exceptionally limited, previously making assessment of their biologic behavior and design of optimal therapy uncertain.

A 37-year-old man with a history of non-Hodgkin lymphoma of the right neck presented with right posterior maxillary sensitivity of at least 6-years’ duration. Radiographically, a partially-corticated, unilocular radiolucency was identified enveloping the roots of the first and second right maxillary molars causing buccal and palatal cortical expansion. The maxillary lesion was excised along with extraction of involved teeth.

Histopathologic examination showed a cystic lesion lined by markedly acanthotic stratified squamous epithelium exhibiting a verrucopapillary architecture with broad, bulbous, rete ridges, prominent luminal parakeratin production and parakeratin cleft formation. Occasional intraepithelial keratin whorls were also present. Cytologic aberrations including basilar crowding, increased nuclear-to-cytoplasmic ratio, hyperchromatism and precocious keratinization were observed. The cyst wall comprised chronically inflamed fibrous tissue. Definite mural invasion was not identified in multiple sections. By immuhistochemistry, p16 staining was patchy, while p53 and Ki67 decorated basal and, focally, suprabasal cells. No recurrence was reported after 14 months of follow-up.

Here, we report an uncommon case of intraosseous AVPEP with VC features developing from the epithelial lining of a keratinizing DOC. Despite their alarming histopathologic appearance, a review of the literature reveals that such lesions tend to have a favorable prognosis following complete surgical excision.