A 14-year-old boy with a history of insulin-dependent type 1 diabetes presented to our dermatology clinic with a 2-year history of a slowly growing discoloration on the right medial knee. He denied associated pruritus or pain, and he had no other medical conditions other than his poorly controlled diabetes. His most recent glycated hemoglobin level was 8.4%. Gross inspection revealed a bilobed, semiannular and confluent, snowman-shaped, atrophic, waxy patch measuring 2.5 × 1.5-cm, with a brown center and a yellow-orange periphery. How would you proceed?