Which condition is characterized by a "apple-core" lesion on colonoscopy?

The condition characterized by an "apple-core" lesion on colonoscopy is colorectal cancer. This term refers to the specific appearance of the lesion as a constricting, irregular mass that causes a narrowing of the colon, resembling the shape of an apple core. This finding is commonly associated with infiltrative tumors that lead to stricture formation in the colon, indicative of advanced malignancies.

Colorectal cancer can frequently present with such lesions, and the "apple-core" appearance is particularly recognized in the context of infiltrative, circumferential lesions affecting the bowel wall. This distinct manifestation during colonoscopy can help differentiate it from other conditions that may present similarly but do not typically exhibit this classic morphology.

In contrast, diverticulitis usually presents with localized inflammation and may not cause the same patterned constriction seen in colorectal cancer. Colonic polyps can generally be seen as protrusions and would not typically appear as strictured lesions, while irritable bowel syndrome predominantly presents with symptom patterns rather than identifiable structural lesions on colonoscopy.