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
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