Verruciform Xanthoma Within the Cyst Lining of Hidradenitis Suppurativa.

Verruciform xanthoma (VX) is a rare lesion most often seen in the oral mucosa or anogenital region, most commonly characterized histologically by verrucous epithelial hyperplasia and foamy histiocytes in the papillary dermis. While VX has been reported in association with inflammatory dermatoses such as lichen planus and lichen sclerosus, its occurrence in the context of hidradenitis suppurativa (HS) has not been previously documented. In this case we present a 56-year-old man with long-standing, Hurley Stage 3 HS affecting the gluteal region. Following surgical excision of a draining sinus tract, histopathology revealed a squamous-lined follicular cyst consistent with HS, with approximately 10% of the cyst lining displaying features characteristic of VX, including papillomatous acanthosis, parakeratosis with neutrophils, and underlying foamy macrophages. Retrospective review of prior HS specimens did not show similar changes. This case expands the histologic spectrum of HS and suggests that chronic inflammation may promote secondary verruciform xanthomatous changes within follicular cysts. Although mutations in the cholesterol biosynthesis gene NSDHL have been linked to VX, no lichenoid or syndromic features were observed in our patient, supporting an inflammatory rather than genetic etiology. Recognition of VX-like changes in HS is important to avoid misdiagnosis as squamous cell carcinoma and further elucidates the complex epithelial remodeling in chronic inflammatory dermatoses.