A man in his 20s presented with a 10-year history of relapsing papules on the antihelix of the left ear. Less frequently, the papules were found on the right ear as well. Sometimes the lesions were painful to applied pressure or when exposed to cold winds.On physical examination, the right external ear showed no abnormalities, and the left antihelix showed 5 yellowish papules with surrounding erythema and scattered telangiectasias, firm in consistency and tender to applied pressure. Each lesion measured 3 to 5 mm in size (Figure, A). There was no history of trauma, infection, insect bites, tuberculosis, or diabetes mellitus. The patient used methylphenidate hydrochloride to treat attention-deficit/ hyperactivity disorder.The lesions were excised to establish a diagnosis. Excision of the lesions was performed under local anesthetic. Both the dermis and underlying cartilage were excised.Histologic examination showed an intact epidermis, without ulceration. Also the cartilage and perichondrium were not histologically abnormal. In the dermis, lesions were found with central degeneration (necrobiosis) of collagen, surrounded by palisading histiocytes. A few lymphocytes were present as well (Figure, B and C). Mucin stains showed the presence of mucin in the necrobiotic foci (arrow) (Figure, D). Periodic acid-Schiff and auraminerhodamine stains remained negative for mycobacteria.What is your diagnosis?