Squamous cell carcinoma at the oral commissure in a patient with Behçet's disease

Lip cancer at the corner of the mouth (i.e., the oral commissure) is considered difficult to detect as the initial lesion, especially in individuals with Behçet's disease (BD), because aphthous stomatitis frequently occurs at the oral commissure of BD patients, but the incidence of cancer at that site is rather low. We present a rare case of oral commissure carcinoma in a 69-year-old Japanese male with BD. The patient's stomatitis had recurred for 10 years, and symptoms of right angular stomatitis had worsened for 2 months. We observed a 10 mm × 6 mm ulcer with induration at the right oral commissure, surrounded by a 20-mm white lesion. The pathological examination of the biopsy sample revealed squamous cell carcinoma. We resected the tumor with the patient under general anesthesia. Although the incidence of carcinoma of the oral commissure is generally low, it is very important to carefully observe patients with BD so that the risk of overlooking this cancer or misdiagnosing it as a recurrent aphthous ulcer is minimized.