COLON CANCER
Epidemiology
• 2nd most common cause of cancer mortality
• Lifetime risk is about 1 in 17
• Industrialized nations have the highest risks
o South America and China are among the lowest
• Blacks > Whites > Asians > Hisp > NA
• M > F (slightly)
• Incidence increases after age 50 (90%)
• 80% are sporadic
Risk factors
• Diet
o Red meat and animal fat
o Folate, fiber, calcium, selenium, fruits and vegetables Æ ?protective
• Smoking and alcohol
• IBD
• Hereditary syndromes
• Previous carcinoma
• Polyps
• Family history
• S. Bovis bactermia
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Anatomy
Location
Adenoma-Carcinoma Sequence
• Larger adenomas harbor cancer more often
• Residual benign tissue found in most cancer specimens
• Benign polyps have been observed to become cancer
• Adenomas occur more frequently in cancer patients
• Adenoma patients have increased lifetime risk of dev. cancer
• Removal of polyps decreases risk
• Populations with cancer have high prevalence of polyps
• FAP Æ 100% cancer
• Peak incidence of adenomas is 50; peak incidence of cancer is
60 Æ suggesting 10-year time span
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Polyps
• Morphology
o Tubular, villous, tubulovillous
Risk of malignancy; 5% - tubular, 22% - tubulovillous, 40% - villous
o Pedunculated, flat (sessile)
Sessile polyp with cancer has 10% chance of lymph node metastasis
• Size
o 0.6 – 1.5 cm = 2% chance of cancer
o 1.6 to 2.5 = 19% chance of cancer
o 2.6 to 3.5 = 43% chance of cancer
o >3.5 cm = 76% chance of cancer
• Hyperplastic polyps
o Most common
o 90% are less than 3mm
o Considered to have no malignant potential
o Adenomatous changes have been found so polyps should be excised
Haggitts: Applies only to pedunculated polyps
• Level 0 – in situ
• Level 1 – head of polyp
• Level 2 – neck
• Level 3 – stalk
• Level 4 – submucosa
• Any sessile polyp is Level 4
• Excision of Level 1-3 with 2mm margin and
NO poor prognostic indicator is sufficient
treatment
Familial Adenomatous Po