Progressive Sclerodermoid Skin Changes —Quiz Case

A previously healthy 51-year-old man presented with asymptomatic brown-pigmented lesions on his first left-hand fingertip. The lesions had appeared 3 months ago and gradually spread. He had no history of tobacco smoking, wearing rings, chemotherapy, or work involving friction or in wet places. On physical examination we found an ill-defined, golden to light brown patch over the left thumb finger-tip (Figure 1). Dermoscopy revealed a parallel ridge pattern (Figure 2). A skin biopsy specimen was obtained and stained with hematoxylin-eosin (Figure 3). What is your diagnosis?