2 IntroductionOverall, colorectal cancer ranks second only to bronchogenic carcinoma among the cancer killers.Adenocarcinomas constitute the vast majority of colorectal cancers and represent 70% of all malignancies arising in the gastrointestinal tract.
3 Terminology•A polyp is a tumorous mass that protrudes into the lumen of the gut; traction on the mass may create a stalked or pedunculated polyp.Alternatively the polyp may be sessile, without a definable stalk.•Non-neoplastic Polypsabnormal mucosal maturation,inflammationdo not have malignant potential (excl.Peutz-Jeghers)•Neoplastic Polyps:adenomatous polyps, or adenomas,precursors of carcinoma.
9 Adenomas Small-pedunculated; large-sessile Colon Malignancy: Familial predispositionRisk of carcinomaSubtypes:TubularVillousTubulovillousMalignancy:Rare: tubular adenoma less than 1 cmHigh: sessile villous adenomas more than 4 cmDysplasia: villous adenomas.
10 Tubulovillous adenomas: Tubular adenomas:Colon (rectosigmoid)Small-sessile; large-pedunculatedStalk is covered by normal mucosaTumor is composed of neoplastic epitheliumIntramucosal Ca or invasive Ca.Villous adenomas:Rectum/rectosigmoidLarger than tubularSessileCauliflower-likeDysplasia Ca.Tubulovillous adenomas:Peduculated or sessileMix of tubular and villous patternsDysplasiaMalignancy.
12 Familial polyposis syndromes Peutz-Jeghers SyndromeMultiple polyps (polyposis coli)large, firm polyps with a tree-like structuredistinctive freckles on the lips, palms, and genitalsrisk for colon cancer.Turcot's syndromeMultiple polypsbrain tumors.Gardner's syndromeMultiple polypsminor birth defectsrisk for other tumors (notably mesenchymal).Cowden's syndromeRisk of tumors of:ThyroidBreastUterusSkin.
15 Small Intestine tumors: Small intestine -75% but tumors – 3-6%Benign tumors (common)Adenoma(25%), lipoma & leiomyoma.Malignant tumors (rare; <1%)Adenocarcinoma of Duodenum or Jejunum, Carcinoid, Lymphoma, SarcomaPresent at late stage, 70% 5 year survival.
20 Colorectal carcinoma Adenocarcinomas (98%) often arises in one of the benign neoplastic colonic polyprisk factors(1) mild hereditary defects in anti-oncogenes lost in colon cancer,(2) years of eating the typical western diet.Low content of vegetablesHigh content of refined carbohydratesHigh content of fat (animal)Low content of micronutrients (vitamins A, C, E).
23 Carcinoid Tumors2% of colorectal malignancies.Origin: Neuroendocrine cells (paracrine, Kulchitsky, enterochromaffin, neurosecretory, chromaffin)Location:gut (common in appendix)pancreas or peripancreatic tissue,lungs,biliary treeliver.Rectal and appendiceal carcinoids almost never metastasizeThe classic carcinoid syndrome (serotonin)(1) wheezing (asthmatic);(2) flushing (vasomotor);(3) fibrosis (cardiac, pulmonic, pleural, pelvic);(4) intestinal hypermotility.
24 Midgut carcinoids: Foregut carcinoids: small intestinal, appendiceal, most colonic carcinoids.These are usually argyrophil (hormonally active).Foregut carcinoids:lung,duodenal,biliary carcinoids.These are almost never argyrophil (hormonally inactive).
26 Gastrointestinal lymphoma Less common than carcinomasWestern lymphomas are usually familiar B-cell lymphomasMediterranean lymphomas usually feature plasmacytoid differentiation (a subset is alpha-heavy chain disease).Sprue-associated lymphoma exhibits T-cell markers