Inverted colonic diverticulum of the cecum mimicking a submucosal tumor: a case report.

backgroundInverted colonic diverticulum (ICD) is a rare endoscopic finding that often mimics a sessile polyp or submucosal tumor, increasing the risk of misdiagnosis and inappropriate intervention. Accurate identification is crucial to avoid potential complications such as perforation. This case is notable for its unusual location in the cecum and its initial misdiagnosis as a gastrointestinal stromal tumor (GIST). CASE PRESENTATION: A 66-year-old man with a 10-year history of chronic constipation underwent routine surveillance colonoscopy, which revealed a 30–40 mm sessile lesion in the cecum near the ileocecal valve with a central depression covered by adherent debris/impacted fecal material and peripheral hyperemia; water-jet irrigation was attempted but failed to adequately clear the adherent material. Biopsies obtained from the peripheral mucosa showed benign mucosal hyperplasia, and contrast-enhanced computed tomography (CT) demonstrated focal cecal wall thickening without definite radiologic evidence of malignancy; however, malignancy could not be confidently excluded given the lesion’s size and indeterminate preoperative assessment. After multidisciplinary team (MDT) discussion and shared decision-making with the patient and family, laparoscopic right hemicolectomy was performed. Gross examination showed a submucosal mass with a narrow-necked cavity connected to the bowel lumen. Histopathology confirmed inverted colonic diverticulum, with no evidence of dysplasia or malignancy. The patient recovered well without complications.

conclusionsThis case highlights the diagnostic challenges of inverted colonic diverticulum, particularly when located in the cecum. Recognition of endoscopic features and cautious interpretation of imaging are essential to prevent unnecessary or harmful procedures. Surgical resection remains a definitive option when malignancy cannot be excluded or endoscopic diagnosis is inconclusive.