Cutaneous horn: get to the bottom of it.

A 62-year-old man presented to our family practice office with a skin lesion that developed over 8-10 months. Over the past 2-3 months the lesion grew more quickly. A 2-3 cm, hard brown projection was noted on the dorsal aspect of his hand. A decision was made to excise the lesion and send it for pathological evaluation. The lesion was found to be a cutaneous horn with invasive squamous cell carcinoma at the base. The margins of the sample were free of cancer cells. Cutaneous horns are raised skin lesions made of dead keratin derived from base keratinocytes. They are frequently found in areas of the body that have had solar exposure. There are a wide variety of histopathological findings at the base of these lesions. They range from benign to premalignant to malignant. Cutaneous horns should be completely excised and sent for pathological evaluation.