Vulgar Verruca or Seborrheic Keratosis: A Clinical Challenge in Tattooed Skin

The development of verrucous lesions within tattoos poses a common diagnostic challenge, primarily between verruca vulgaris and the rarely reported phenomenon of Koebner-induced seborrheic keratosis (SK). We present the case of a 47-year-old man with a history of pemphigus vulgaris who developed multiple, brown, warty papules meticulously following the pattern of existing black ink tattoos on his trunk and shoulder. Dermoscopy revealed a cerebriform pattern with fissures, ridges, and milia-like cysts, classic for SK. Histopathological examination confirmed the diagnosis, demonstrating acanthosis, papillomatosis, hyperkeratosis, and corneal pseudocysts. No significant hypergranulosis or dilated capillaries within the dermal papillae were observed. Although HPV genotyping was not available, the overall clinicopathologic correlation supported a diagnosis of SK. This case highlights that SK may arise along tattoo tracts through trauma-related mechanisms and should be carefully distinguished from verruca vulgaris to avoid misdiagnosis and unnecessary interventions.