Derm Dx: Hyperkeratotic central plaque on the arm

A 58-year-old male presents for evaluation and treatment of a lesion on his arm that was first noted approximately 4 months ago and that has continued to enlarge in size. He denies antecedent trauma, localized infection, history of similar lesions, and systemic disease. The site is asymptomatic. Physical examination reveals a slightly elevated hyperkeratotic central plaque of 0.6 cm overlying ...