Colorectal Cancer

Epithelial tumors of the intestines. Major cause of morbidity and mortality worldwide. Colon, including rectum: host to more primary neoplasms than any other organ in the body.
Types

Non-neoplastic Polyps

  • Hyperplastic polyps
  • Hamartomatous polyps
  • Juvenile polyps
  • Peutz-Jeghers polyps
  • Inflammatory polyps
  • Lymphoid polyps
Colorectal cancer

Neoplastic Epithelial Lesions

  • Benign polyps
  • Adenomas
  • Malignant lesions
  • Adenocarcinoma
  • Squamous cell carcinoma of the anus

Other Tumors

  • Gastrointestinal stromal tumors
  • Carcinoid tumor
  • Lymphoma
Causes

Genetic influences

  • Preexisting ulcerative colitis or polyposis syndrome
  • Hereditary nonpolyposis colorectal cancer syndrome (HNPCC, Lynch syndrome) → germ-line mutations of DNA mismatch repair genes

Environmental influences:

  • Dietary practices
    • Low content of unabsorbable vegetable fiber
    • Corresponding high content of refined carbohydrates
    • High fat content
    • Decreased intake of protective micronutrients (vitamins A, C, and E)
  • Use of Aspirin® and other NSAIDs: protective effect against colon cancer

Cyclooxygenase-2 & Prostaglandin E2

Symptoms
  • May remain asymptomatic for years
  • Symptoms develop insidiously
  • Cecal and right colonic cancers:
    • Fatigue
    • Weakness
    • Iron deficiency anemia
  • Left-sided lesions:
    • Occult bleeding
    • Changes in bowel habit
    • Crampy left lower quadrant discomfort
  • Anemia in females may arise from gynecologic causes, but it is a clinical maxim that iron deficiency anemia in an older man means gastrointestinal cancer until proved otherwise
  • Spread by direct extension into adjacent structures and by metastasis through lymphatics and blood vessels
  • Favored sites for metastasis:
    • Regional lymph nodes
    • Liver
    • Lungs
    • Bones
    • Other sites including serosal membrane of the peritoneal cavity
  • Carcinomas of the anal region → locally invasive, metastasize to regional lymph nodes and distant sites

Treatment

  • Chemotherapy
  • Radiotherapy
  • Photodynamic therapy
  • Radical surgery
  • Gene therapy