One of a Kind: Adenomyoma in a Rectal Polyp

Adenomyoma is a rare manifestation of extrauterine Müllerian pathology and is infrequently described within the gastrointestinal tract. We report a 60-year-old woman with a 10 mm rectal polypoid lesion initially unresectable by standard techniques. Endoscopic ultrasound demonstrated a subepithelial lesion involving the muscularis propria, and fine-needle aspiration was nondiagnostic. Endoscopic full-thickness resection achieved complete removal. Histology revealed adenomyoma with endometrial glands, stroma, and smooth muscle. This case highlights the diagnostic challenge of atypical subepithelial lesions and demonstrates endoscopic full-thickness resection as an effective, minimally invasive approach for definitive diagnosis and management.