A 13-year-old girl presented with a cut on her left foot that had been worsening for two weeks. The initial small scrape was immediately treated with neomycin ointment and covered. There was minimal pain at the site, but the patient had a low-grade fever the day before presentation. She had no bowel or bladder symptoms or joint pain. Her medical history included acne, seasonal allergies, and asthma.

Physical examination revealed a mildly tender ulcerative lesion measuring 3 × 3 cm on the dorsal aspect of the left foot (Figure 1). The lesion had raised borders with minimal surrounding erythema and induration. It had overlying eschar but no purulent discharge. The patient was afebrile, with normal heart rate and blood pressure. Laboratory test results were normal, including complete blood count, rheumatoid factor, complete metabolic panel, antinuclear antibody, and anticyclic citrullinated antibody.

Question

Based on the patient’s history and physical examination findings, which one of the following is the most likely diagnosis?

• A. Allergic contact dermatitis.

• B. Nummular dermatitis.

• C. Pyoderma gangrenosum.

• D. Squamous cell carcinoma.