Polyps of the Small & Large Intestine

Colonic Polyps may be Inflammatory, Hamartomatous, Hyperplastic, or Neoplastic

Neoplastic

Tubular Adenomas – with low grade/high grade dysplasia/?Invasive focus. Tubular, Tubular Villous or Villous Adenomas. Characterised by hyperchromasia, elongation & stratification.

Serrated lesions – Sessile serrated polyp/ Sessile serrated adenoma. Typically in the right colon. Assoc with microsatellite instability. Characterised by serrated architecture thoroughout the full length of the crypt (vs serration confined to the surface in hyperplastic polyps), Lateral boot shaped broad crypt bases and crypt dilation.

Intramucosal carcinoma (terminology not typically used in UK)- Invasion into the lamina propria or muscularis mucosae. No lymphatics so little or no metastatic potential.

Adenocarcinoma (if into the submucosa)- Kikuchi level (Sessile tumours) & Haggitt level  (Polypoid tumours)

Hyperplastic Polyps – Benign polyps with serrated architecture on the surface.

Inflammatory

Inflammatory Fibroid Polyp – Typically in the small intestine & stomach. Lesion within the submucosa with a loose connective tissue stroma containing eosinophils & plasma cells. The ulcerated surface is covered by granulation tissue. Stellate or spindle shaped fibroblasts within the lesion are arranged in concentric rings around arterioles.

Inflammatory Cap Polyp/ Inflammatory Cloacogenic Polyp/Solitary Rectal Ulcer – All names for mucosal prolapse characterised by glands distorted by prominent smooth muscle proliferation +/- ulceration. Typically in the anterior wall of the rectum and assoc with rectal bleeding & mucus discharge.

Inflammatory Pseudopolyps – Typically seen in UC.

Hamartomatous

Juvenile Polyps – May be sporadic or syndromic. The vast majority occur in children less then 5 yrs and in the rectum. Characteristed by cystic spaces formed from dilated glands which contain inflammatory debris and mucin. The lamina propria may have a mixed inflammatory infilatrate and the surface eroded. With the autosomal dominant syndrom juvenile polyposis there may be 100s of polyps.

Peutz-Jeghers Syndrome – Autosomal dominant condition occuring typically at about 11 years assoc with multiple polyps and mucocutaneous pigmentation. Polyps have a characteristic arborizing pattern of connective tissue & smooth muscle surrounding complex glandular architecture although with normal appearing intestinal epithelium. Increased risk of malignancy (Colon, pancreas, breast, lung, ovaries, uterus, testicles)

Cowden Syndrome – Autosomal dominant assoc with loss of function mutation of PTEN (tumour suppressor). Characterised by macrocephaly, multiple GI polyps and benign skin tumours. Increased risk of breast carcinoma, follicular carcinoma of the thyroid and endometrial. But not GI!

Cronkhite-Canada Syndrome – Non hereditary and typically >50 years. Polyps similar to juvenile polyps. The intervening mucosa shows cystic crypt dilatation & lamina propria oedema. Assoc with nail atrophy, hair loss & cutaneous pigmentation. 50% of cases are fatal.

References:

Rosai & Ackerman’s. Surgical Pathology. 9th Ed.

Fletcher. Diagnostic Histopathology of Tumours. 3rd Ed.

Robbins & Cotran. Pathologic Basis of Disease.

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