The radiological hallmarks of the classic colonic “apple core” lesion are: a relatively short, sharply defined region of circumferential, annular, constricting colonic narrowing with overhanging margins; ulcerated mucosa; and an eccentric and irregular lumen. In the case of any annular “apple core” colonic lesion, adenocarcinoma is the diagnosis to be excluded.

The differential diagnosis includes: malignant neoplasms, usually adenocarcinoma or, less commonly, lymphoma; inflammatory disorders, most commonly diverticulitis, also chronic Crohn’s disease or chronic ulcerative colitis; vascular disorders, like ischemic colitis; infectious etiologies, including Chlamydia infection (lymphogranuloma venereum), Tuberculosis, Helminthoma, or Ameboma; or benign neoplasms (villous adenoma).

Cases of colonic adenocarcinoma presenting as "apple core" lesions frequently are detected either on routine screening colonoscopy or during investigative colonoscopy in patients with signs and symptoms suggestive of the diagnosis. Occasionally, they are initially detected on abdominopelvic computed tomography performed for evaluation of vague abdominal complaints and/or systemic symptoms. Colonoscopic biopsy establishes definitive tissue diagnosis.