Colorectal Carcinoma (Colon Cancer) Lecture Notes

Introduction

• Colorectal Carcinoma: Malignant cells in the large intestines (colon and rectum).
• Significance: Most common GI tract cancer, major cause of death worldwide.

Anatomy of the Large Intestine

• Abdominal Cavity Spaces:
  • Intraperitoneal: Contains duodenum, small intestines, transverse and sigmoid colon, rectum.
  • Retroperitoneal: Contains distal duodenum, ascending/descending colon, anal canal.
• Layer Composition:
  • Serosa/Adventitia: Outermost layer.
  • Muscular Layer: Moves food through bowel.
  • Submucosa: Contains blood vessels, lymphatics, nerves.
  • Mucosa: Inner layer, direct contact with food, contains intestinal glands.

Pathogenesis

• Origin: Most are adenocarcinomas from intestinal gland cells.
• Mutations: Usually sporadic; some familial genetic mutations (e.g., APC gene).
• APC Gene: Tumor suppressor, mutations lead to polyps and potentially malignant tumors.
• DNA Repair Gene Mutations: Allow accumulation of mutations, polyp formation.

Types of Polyps

• Pre-malignant/Neoplastic Polyps: Adenomas and serrated polyps.
• Adenomatous Polyps: APC mutation, look like normal mucosa cells.
• Serrated Polyps: Defects in DNA repair genes, sawtooth appearance.

Staging of Cancer

• Stage 0: Carcinoma in situ, confined to mucosa.
• Stage 1: Grown beyond mucosa, no lymph node/distant spread.
• Stage 2: Invasion of colonic/rectal wall, possibly nearby organs.
• Stage 3: Spread to lymph nodes.
• Stage 4: Metastatic, spread to distant organs (liver, lungs).

Risk Factors

• Non-modifiable: Age (elderly), gender (male), inflammatory bowel disease.
• Modifiable: Smoking, red meat consumption, low fiber diet, obesity.
• Associated Disorders: Familial adenomatous polyposis, hereditary non-polyposis colorectal cancer.

Symptoms

• Right Colon Tumors: Outward growth, vague pain, weight loss, late diagnosis, potential bleeding.
• Left Colon Tumors: Infiltrating masses, bowel obstruction, early symptoms, colicky pain, hematochezia.

Diagnosis

• Colonoscopy: Visual and biopsy of polyps.
• Fecal Occult Blood Testing: Detect gastrointestinal bleeding.
• Tumor Marker (CEA): Elevated in colorectal cancer.
• Barium Enema: X-ray for abnormalities, apple-core sign.
• Early Detection: Routine colonoscopy and fecal tests, especially in high-risk individuals.

Treatment

• Early Stage: Surgical resection.
• Advanced Stage (Lymph Nodes): Chemotherapy.
• Metastatic Cancer: Typically incurable, palliative care with chemotherapy or surgery.

Recap

• Key Points: Common and deadly cancer, sporadic cases, modifiable risk factors.
• Symptoms Vary: Based on tumor size/location.
• Prevention: Focus on early detection and lifestyle changes.

Goal: Aid clinicians in learning, retention, and thriving.