(BMJ)—A 41-yo man presented w/ a 5-mo hx of a painless, nonpruritic lesion on his L hand, where he had liquid nitrogen tx for a common wart 6mo prior. Exam: annular, verrucous plaque on dorsum of L hand, w/ atrophic scar and normal skin in the center. What is the dx?
Squamous cell carcinoma
Doughnut wart
Lichen planus
Tinea corporis
Tuberculosis verrucosa cutis
You are correct. The black and red dots on the surface of the verrucous plaque indicate a common cutaneous wart, and the morphology of the lesion suggests a doughnut wart. These warts are a complication after tx w/ cantharidin or cryotherapy, and are a form of recurrent warts, w/ central clearing and peripheral recurrence forming a doughnut shape. The pathogenesis is unknown, but seems to represent an intraepidermal autoinoculation of the wart virus through the blister cavity. The pt was treated w/ topical 5% 5-fluorouracil. The lesions resolved in 2mo and had not recurred during a year of f/u.

BMJ 2020;370:m2209