A 17-year-old high school baseball player presented to a sports medicine clinic for left anterior knee pain. During the exam, a hyperpigmented lesion was incidentally noted on his left palm. The patient, who also played basketball and football, was unsure of how long he’d had the lesion, and he did not recall having any prior lesions on his hand. He denied any discomfort or significant past medical history. There was no known family history of skin cancers, but the patient did report that his brother, also an athlete, had a similar lesion on his hand.
On closer examination, scattered black dots were noted within a 2 × 1–cm thickened keratotic plaque at the hypothenar eminence of the patient’s left hand (Figure). There was no tenderness, erythema, warmth, or disruption of normal skin architecture or drainage.
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