Carcinogenesis is the development of cancer and the substances causing cancer are referred to as carcinogens. The external agents responsible for cancer are categorized as-
- Physical carcinogens- radiation such as X-ray, UV-ray which causes chromosomal breakage, DNA alterations.
- Chemical carcinogens- ethidium bromide, asbestos, arsenic, components of tobacco smoke etc. Tobacco use is the most important risk factor comprising 22% deaths.
- Biological carcinogens- infections from certain viruses, bacteria and parasites. Viral infections including papillomavirus, hepatitis-B & C virus, Epstein- Barr virus, HIV and others are responsible for one-fourth death cases.
Other risk factors are-
- Poor diet
- Lack of exercise
- Excessive drinking
- Several disease complications
- Epigenetic change
- Heredity or family history of genetic defects (5-10% cases).
Not a single cause accounts for the development of cancer, rather it is a multistep process where multiple factors contribute to its progression.
Diagnosis is important to understand the specific type of cancer so that the treatment becomes easier and lives can be saved. Laboratory test (blood test, urine/feces test), endoscopy (visual examination of the interior of a hollow body organ), tumor biopsy (physical examination of tissue or body fluid) and imaging are performed to diagnose cancer.