Large Verruciform Xanthoma in an Unusual Anatomic Location Mimicking Squamous Cell Carcinoma: A Diagnostic Pitfall. Erem AS, Brahmbhatt M, Parker DC. Erem AS, Brahmbhatt M, Parker

Summary: A sporadic verruciform xanthoma is an infrequent lesion that occurs predominantly in males, typically in the fifth and sixth decade, and presents in the oral mucosa and anogenital region. Other cutaneous sites of involvement are rare. While some subsets of reported cases are associated with immunosuppression, dermatological, traumatic, and systemic conditions in males, the etiology of this entity remains unknown. Verruciform xanthoma has an excellent prognosis, and recurrence is extremely rare. We report a 63-year-old African American male with no significant past medical history who presented with a 6.5 cm fungating, exophytic plaque on the chest wall. It reportedly began as a "bump" and then grew rapidly and ulcerated within a few months. The clinical diagnosis was squamous cell carcinoma. The preliminary pathologic diagnosis on biopsy was squamous cell carcinoma, followed by intradepartmental consultation with the dermatopathology department. The histopathologic findings showed an exophytic, verrucous, squamous proliferation with cystic and proliferative features. The verrucous squamous proliferations were characterized by eosinophilic parakeratosis extending deep between epithelial papillae. Numerous xanthoma cells were present in the dermis adjacent to the verrucous squamous proliferations. The findings were consistent with verruciform xanthoma. This case illustrates a critical diagnostic pitfall and the importance of considering verruciform xanthoma in cases where the clinical differential diagnosis includes squamous cell carcinoma.