Large bowel neoplastic polyps
A polyp is defined as a tumour attached by a stalk to the surface from which they arise. Neoplastic polyps of the colon are also known as adenomas.
Affects 5–10% of the population in the Western world.
Sporadic cases increase with age.
Polyps may be solitary (sporadic) or multiple, e.g. familial adenomatous polyposis. Neoplastic polyps may be tubular, villous or tubular-villous dependent on histological features.
Tubular polyps account for 90% and consist of glandular tubules with a fibrovascular core covered by a mucous membrane.
Villous adenomas are composed of finger like epithelial projections, spread over a large area within the mucosa.
Tubular villous adenomata are composed of both patterns.
Most are asymptomatic but they may cause bleeding and diarrhoea.
All neoplastic polyps are pre-malignant, low lesions may prolapse through the anus.
Tubular polyps are resected endoscopically, villous lesions require transmural excision or formal resection.
There is a 30–50% risk of recurrence therefore surveillance with 3–5 yearly colonoscopy in patients under 75 years is suggested.