A 47-year-old Hispanic man first noticed an asymptomatic growth on the extensor surface of his left forearm 5 years before presentation. He subsequently had similar growths on his hands and forearms. His medical history was notable for keratinizing squamous cell carcinoma of the bladder 4 years earlier. The tumor was completely resected, and there was no pathologic evidence of metastasis. Generally, the patient was in good health, and a review of systems revealed no abnormalities. His occupational history included chicken processing and work with cement, paint, and tobacco. He had no known exposure to cutting oils or tar.