Colorectal Cancer

Colorectal cancer (CRC) is a malignant neoplasm arising from the colon or rectum, often developing from adenomatous polyps through a multistep process involving genetic and epigenetic alterations.

Definition

Colorectal cancer (CRC) is a malignant neoplasm arising from the colon or rectum, often developing from adenomatous polyps through a multistep process involving genetic and epigenetic alterations.

Epidemiology

Third most common cancer worldwide and second leading cause of cancer death
Higher incidence in developed countries due to lifestyle factors
Peak incidence: 60–70 years
Slight male predominance
Incidence rising in younger adults (<50 years) in some regions

Etiology

Sporadic: majority of cases (~70–80%)
Hereditary syndromes: Lynch syndrome (HNPCC), Familial Adenomatous Polyposis (FAP)
Lifestyle factors: high red/processed meat intake, low fiber diet, obesity, sedentary lifestyle, smoking, alcohol
Inflammatory bowel disease: ulcerative colitis, Crohn's disease increase risk
Genetic mutations: APC, KRAS, TP53, mismatch repair genes

Pathophysiology

Adenoma-carcinoma sequence: normal epithelium → adenoma → carcinoma
Accumulation of genetic mutations in oncogenes and tumor suppressor genes
Chromosomal instability, microsatellite instability, CpG island methylator phenotype contribute to tumor progression
Local invasion into muscularis propria, submucosa, and adjacent structures
Metastasis: regional lymph nodes, liver (most common), lungs, peritoneum