Plantar warts recently turned black. Clinical and histopathologic findings.

The inflammatory component associated with blackening and subsequent regression of plantar warts has been little appreciated in the literature. Two patients with plantar warts in whom one of the warts showed prominent, clinically evident inflammation were observed. Blackening and subsequent regression of all plantar warts then occurred. In one patient, microscopic examination of biopsy specimens of two lesions that were taken within 24 and 72 hours, respectively, after they had turned black demonstrated the following histologic findings: blood clots and hemorrhage in the stratum corneum, degeneration and necrosis of epidermal cells, eosinophilic cytoplasmic masses within degenerating epidermal cells, thrombosis of superficial and deeper dermal blood vessels, a mononuclear cell infiltrate in and around dermal blood vessels, and a mixed polymorphonuclear and lymphocytic infiltration in the areas of hemorrhage and degenerating epidermis. This constellation of histopathologic changes suggests that involution was in progress long before blackening of the warts occurred.