Carcinogenesis
![Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.](/Images/godic/202502/18/Cancer_requires_multiple_mutations_from_NIHen2556.png")
![The central role of DNA damage and epigenetic defects in DNA repair genes in carcinogenesis](/Images/godic/202502/18/Diagram_Damage_to_Cancer_Wiki_300dpi.svg2556.png")
![Longitudinally opened freshly resected colon segment showing a cancer and four polyps. Plus a schematic diagram indicating a likely field defect (a region of tissue that precedes and predisposes to the development of cancer) in this colon segment. The diagram indicates sub-clones and sub-sub-clones that were precursors to the tumors.](/Images/godic/202502/18/Image_of_resected_colon_segment_with_cancer_&_4_nearby_polyps_plus_schematic_of_field_defects_with_sub-clones2556.jpg")
![Tissue can be organized in a continuous spectrum from normal to cancer.](/Images/godic/202502/18/Cancer_progression_from_NIH2556.png")
Carcinogenesis or oncogenesis or tumorigenesis is the actual formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by a progression of changes at the cellular, genetic, and epigenetic level that ultimately reprogram a cell to undergo uncontrolled cell division, thereby forming a malignant mass.