The ProblemA 44-year-old Caucasian woman presents to her primary care physician with a report that she had traumatized a pigmented lesion on the back of her calf while exiting an automobile, with the result that the previously enlarging lesion had now completely disappeared. Physical examination reveals a well-healed 4-mm circular scar on the back of the leg with no visible hypopigmentation, hyperpigmentation, or palpable nodularity. No popliteal or inguinal adenopathy is noted and no clinically...