Question 1:
A 63-year-old woman with peripheral vascular disease, chronic kidney disease stage III, and COPD was referred to dermatology by vascular surgery for a 4-week history of a painful, intermittently pruritic and slowly enlarging rash on the left inner thigh. The patient reported several healing ulcers within the rash but denied any blistering or pustules. No other mucocutaneous lesions were present. She denied similar episodes previously. She was given two courses of antibiotics from her primary care physician for suspected cellulitis with no improvement. A CT scan of the patient’s left leg was performed showing occlusion of the left common and external iliac arteries. Her medications included sertraline, losartan, and bupropion. With the exception of a recent increase in dosing of the sertraline, she denied changes in medications or new medications.
Physical exam revealed a large, indurated, erythematous and violaceous plaque with retiform erythema at the periphery involving the left inner thigh. Several healing ulcers were noted. A telescoping punch biopsy was taken of the center of the lesion.
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Figure 1
Figure 2
Figure 3: H&E, 2x
Figure 4: H&E, 10x
Figure 5: H&E, 20x
Figure 6: H&E, 2x
Given these initial findings, which of the following immunohistochemical stains is most likely to be positive in this case?