An African American male in his 70s presented with a 2-month history of discoloration and bleeding on his right third toe. Physical examination revealed a black and red, hyperkeratotic scaly thin plaque with irregular borders on the proximal and lateral nail folds of the right third toe (Figure).
Two nail unit punch biopsies were performed and showed full-thickness disorganization and atypia of epidermal keratinocytes with hyperpigmentation. Fontana-Masson staining highlighted pigmentation within the epithelium and superficial dermal melanophages. A human papillomavirus (HPV) cocktail immunohistochemical stain yielded negative results. These features were consistent with pigmented Bowen disease (BD) of the nail unit. The tumor was removed with clear margins via Mohs micrographic surgery (MMS) and repaired with a full-thickness skin graft harvested from the right groin. The MMS procedure did not reveal any invasive tumor.
Lewis DJ, Miller CJ, Rubin AI. Pigmented Bowen Disease of the Nail Unit. JAMA Dermatol. 2022;158(8):949. doi:10.1001/jamadermatol.2022.2030
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