A 30-year-old man with a history of Crohn disease has noted the appearance of a painful red nodule on his left lower leg during the past week. On physical examination, his temperature is 37.3°C. There is a 0.4-cm, dark red nodule that is very tender to palpation and has a surrounding 5-cm diameter area of paler red skin. Over the next 3 weeks, this lesion resolves, but another develops on the opposite calf. A skin biopsy of the second lesion is done, and microscopic examination shows a dermal mixed inflammatory infiltrate with neutrophils, round cells, and giant cells with pronounced edema. These lesions resolve without scarring, but more lesions develop during the next year. What is the most likely diagnosis?
□ (A) Acne vulgaris
□ (B) Dysplastic nevus
□ (C) Erythema nodosum
□ (D) Impetigo
□ (E) Keratoacanthoma
□ (F) Molluscum contagiosum