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Risk Factors: Familial adenomatous polyposis + variants- < 1 % of CRC. Hereditary nonpolyposis colorectal cancer (HNPCC)- 1-5 % of CRC. Personal or family history of sporadic cancers or adenomatous polyps. Pancolitis - 10x relative risk. L-sided IBD - 3x relative risk. Diabetes mellitus and insulin resistance - ?Insulin is a colonic cell growth factor. Cholecystectomy- inc. rate of R sided cancers in some reports. Alcohol- increased risk due to decreased folate intake and absorption. Obesity- 1.5x relative risk. Coronary Artery Disease- associated with advanced adenomas. Cigarette Smoking- Increased incidence and mortality from colorectal cancer. Ureterocolic anastomoses- Increased risk of neoplasia in close proximity to the ureteric stoma. Acromegaly- Inc. risk of GI cancer and colonic adenomas (more likely multiple adenomas and proximal to the splenic flexure. Red meat- Assoc with CRC esp L sided. Coffee/Tea- Relationship unresolved. Radiation treatment- Inc risk if hx of prostate radiotherapy. Barretts - Conflicting Data. Infections- Mixed and inconclusive. Implicated bugs include Hpylori, Streptococcus bovis, JC virus, HPV, and possibly HIV. Hodgkins- Association with prior Hodgkin’s treatment.
Protective Factors: Diet -High in fruits and vegetables and low in red meat, animal fat and/or cholesterol. Fibre- the role isuncertain. Folic acid- unclear association. Vitamin B6 (pyridoxine) - this demonstrates a protective effect as per The Nurses' Health study. Calcium- adequate levels are protective. Magnesium . Physical activity- exercise is protective. Aspirin and NSAIDs- may be protective by reducing COX-2 driven tumour growth. Combination therapy with DFMO ( irreversible inhibitor of ornithine decarboxylase) and sulindac gives a significant reduction in adenoma rate. Hormone replacement therapy- may reduce risk. Statins - Data are conflicting. Antioxidants - No convincing protective effect. Omega 3 fatty acids -May be protective. Garlic -May be protective.
Polyp stalk Sessile polyps are so called if the base is attached to the colon wall. Pedunculated polyps are so called if a mucosal stalk is interposed between the polyp and the wall. Small polyps (<5 mm, also known as "diminutive polyps") are rarely pedunculated.
Polyp height Flat polyps- have a height < 1/2 diameter of the lesion and are more common in the R colon. Depressed polyps occur in 1%- high risk for HGD / malignancy even if small.
Tubular adenomas > 80 % of colonic adenomas Characterized by a network of branching adenomatous epithelium. Tubular component of at least 75 %. Villous adenomas 10 % of adenomas. Histol: long straight glands that extend from surface to the center of the polyp. Villous component of at least 75 %. Tubulovillous adenomas 5 to 15 % of adenomas. 10 % of adenomas. Has 26 to 75 % villous component. Serrated adenoma — Benign. MIxed hyperplastic and adenomatous elements. Have a malignant potential- Likely precursor lesions to sporadic MSI CRC. Varieties of serrated adenomas Sessile serrated adenoma in hyperplastic polyposis. Admixed hyperplastic polyp/adenomatous polyps, which can be conceived as a "collision" of a traditional adenoma and a hyperplastic polyp.
Polyp dysplasia All adenomas are dysplastic. Polyps are classified pathologically as high (which includes carcinoma in situ or low grade).
Colonic Polyps Adenomas (70% of all polyps) and hyperplastic polyps are the most frequently found. Adenomas have a variable appear - ance and are usually redder than the surrounding tissue but may be normal in colour or even yellow. There may be pedunculated, sessile, flat or carpet-like and the surface smooth, velvety/villous, lobular or nodular.
Other polyps types
Things that look like polyps: Mucosal prolapse in the sigmoid colon. Inverted appendix or appendix stump.
Submucosal lymphoid- Pneumatosis Cystoides Intestinales- Colitis cystica profunda- Lipoma-are pale, yellowish and often demon - strate the pillow sign. Removal should not be attempted unless the patient is symptomatic. Carcinoid Mets Leiomyoma Haemangioma Fibroma Endometriosis Epithelial Non malignant Mucosal Hyperplastic- Pale and smooth with vivible surface vessels. Flat or sessile but may be pedunculated. They may disappear on luminal distension. Inflammatory Hamartoma Epithelial Neoplastic Tubular (85%) Tubulovillous (15%) Villous (5%)
CRC incidence of 0.5 %/yr if disease duration 10-20 years, then 1%/yr . Worse if also have PSC
Related to reduced expression of PPAR gene
Features suggesting malignancy: Ulceration. Surface irregularity with depression. Convergence of folds or expansion of the normal tissue adjacent to the lesion. Friability. A failure of the lesion to lift away from the colonic wall (the non-lifting sign).
Punctuate erythema and petechiae and the gradual change in colour from the tip to the base suggests this diagnosis.
Glandular Architecture
Written by Dr Sebastian Zeki