The colorectal adenoma is a benign glandular tumor of the colon and the rectum.

It is a precursor lesion of the colorectal adenocarcinoma (colon cancer).

Villous adenomas have been demonstrated to contain malignant portions in about 15–25% of cases, approaching 40% in those over 4 cm in diameter.

These can also lead to secretory diarrhea with large volume liquid stools with few formed elements.

They are commonly described as secreting large amounts of mucus, resulting in hypokalaemia in patients.