Definition
Colon cancer is a malignant tumor that develops in the mucosa of the colon or rectum. It is one of the most common cancers worldwide but is often curable if diagnosed early.

Pathogenesis
Cancer development is linked to genetic mutations and environmental factors. Polyps, especially adenomatous polyps, can develop into cancer if not removed. Risk factors include age, family history, diets high in red and processed meat, low fiber intake, and inflammatory bowel diseases.

Diagnosis
Diagnosis is made via colonoscopy, allowing direct observation and biopsy. Stool tests for hemoglobin or DNA can be used for screening. Imaging techniques, such as CT or MRI, help assess cancer spread.

Treatment
Treatment depends on the cancer stage:

  • Endoscopic or surgical removal: The main treatment in early stages.
  • Chemotherapy: Used in advanced stages or post-surgery to reduce recurrence risk.
  • Radiotherapy: Common in rectal cancer, applied before or after surgery.
  • Immunotherapy: For cancers with specific genetic mutations.

Prevention
Regular screening (colonoscopy starting at age 45 or earlier for those with family history) is critical for early detection of precancerous lesions. A healthy lifestyle, a diet rich in fiber and low in processed foods, and avoiding smoking and alcohol reduce cancer risk.

Early diagnosis and appropriate treatment significantly increase survival rates.

Removing polyps is how screening prevents cancer. A practical example is the removal of multiple pedunculated polyps in a single session.

Key figures: Screening begins at 45. After a normal examination the next colonoscopy is usually at 10 years. After removal of an adenoma of 10 mm or more, high grade dysplasia, or 5 or more adenomas, surveillance is at 3 years. Serious complications of colonoscopy occur in fewer than 3.5 per 1,000 procedures.

Screening is performed with colonoscopy, during which polyps are removed in the same session. Risk is also raised in long standing inflammatory bowel disease.

Frequently asked questions

At what age should colorectal cancer screening begin?

For people at average risk, screening starts at 45, regardless of sex. It begins earlier and is repeated more often in those with a family history of colorectal cancer or polyps, a hereditary syndrome, or inflammatory bowel disease. Colonoscopy is the only method that both detects and prevents, because polyps are removed during the same procedure.

What are the early symptoms?

Early stages are usually silent, which is precisely why screening matters. When symptoms appear they include a persistent change in bowel habit, blood in the stool, unexplained weight loss, iron deficiency anaemia and abdominal pain. Any of these warrants investigation without delay, at any age.

How long does it take for a polyp to become cancer?

The adenoma to carcinoma sequence typically takes years, which is what makes screening effective. Removing an adenoma interrupts that sequence before cancer develops. The surveillance interval after polypectomy depends on the number, size and histology of the polyps removed.

Sources


Content last updated: September 2026 (15/09/2026).