The Actinomyces, a resident flora in the oral cavity, can form a mass in the head and neck region that is often difficult to distinguish from a malignant tumor. This report describes a case of actinomycosis in a 65-year-old man who underwent concurrent chemoradiotherapy, left cervical lymph node dissection, laryngopharyngoesophagectomy, and esophageal reconstruction with the pectoralis major muscle for treatment of hypopharyngeal carcinoma. He subsequently developed a suspicious mass at the pharyngeal stump that was difficult to distinguish from recurrent carcinoma. After two biopsies, treatment with a penicillin antibiotic, and strict follow-up, the mass disappeared 38 weeks after the start of antibiotic treatment. Antibiotic treatment was subsequently discontinued and no recurrence has been detected to date.
