Tinea nigra masquerading as acral lentiginous melanoma.

Tinea nigra is a superficial mycosis that may mimic serious pigmentary lesions. A lesion recently encountered on the foot was suspected of being a malignant melanoma. Histologic and mycologic studies, done after a biopsy was obtained, demonstrated Exophilia werneckii in the stratum corneum. Tinea nigra should be considered in the diagnosis of pigmented lesions of the hands and feet. A KOH examination is a simple and rapid means of demonstrating this entity.