Abstract
Esophageal actinomycosis is a rare, chronic granulomatous disease caused by Actinomyces species. Endoscopy and biopsy are essential for making a diagnosis. This paper reports a case of esophageal actinomycosis that developed after an endoscopic mucosal resection (EMR) for a subepithelial tumor (SET). A 74-year-old male patient had a 3 cm flat, smooth elevation in the esophagus without symptoms. The SET was partially resected, and histology revealed "nonspecific degenerated mesenchymal tissue". Three months later, the patient exhibited a persistently large ulceration at the EMR site, and a biopsy revealed actinomycosis. CT of the chest and abdomen revealed no abnormal findings. Ampicillin treatment was administered for six months, and the ulceration on the esophageal SET improved.