Review Question - QID 109998

A 41-year-old woman presents to her primary care provider with a skin lesion on the back of her neck. The lesion is not itchy or painful. She believes the lesion is new. Her past medical history is notable for generalized anxiety disorder for which she takes fluoxetine. She has had occasional diarrhea, increased flatulence, and worsening fatigue over the past 2 years. She has a 10 pack-year smoking history and drinks 3-4 glasses of wine per day. Her temperature is 99°F (37.2°C), blood pressure is 130/75 mmHg, pulse is 90/min, and respirations are 18/min. Her BMI is 21 kg/m^2. A notable skin finding is shown in Figure A. An immunohistochemical analysis of this lesion would most likely reveal elevated levels of which of the following?