Verrucous Variant of Bowen Disease

Bowen's disease (BD), or squamous cell carcinoma in situ, is a common cutaneous neoplasm with an incompletely understood etiopathogenesis often linked to human papillomavirus (HPV). While the classic presentation is an erythematous macule, rare variants such as verrucous BD exist and can pose significant diagnostic challenges.

We present the case of a 91-year-old woman with a long-standing, 25 mm yellowish, verrucous lesion on her left leg. Clinically, the lesion was highly suggestive of verrucous carcinoma, leading to surgical excision. Histopathological examination revealed an exophytic verrucous tumor without dermal invasion. High magnification showed full-thickness architectural disarray, cytological atypia, and pagetoid spread. Immunohistochemical studies demonstrated strong, diffuse positivity for p16 and Ki67 across all epidermal layers, while p53 was negative. These findings confirmed a diagnosis of the verrucous variant of BD.

Verrucous BD is a rare subtype that is easily misdiagnosed as verrucous carcinoma, an infiltrative neoplasm generally considered unrelated to HPV. Differentiation is critical, as verrucous BD often shows a strong association with high-risk HPV types. Immunohistochemistry serves as a vital tool; intense p16 expression is a highly suggestive marker for HPV-related BD, whereas verrucous carcinoma typically shows low or absent p16 expression.

This case highlights the importance of considering verrucous BD in the differential diagnosis of exophytic, hyperkeratotic lesions. Accurate identification through histopathology and immunohistochemical markers like p16 is essential to distinguish this in situ variant from more aggressive, invasive entities like verrucous carcinoma.