Cancer Development

Cancer is a cluster of more than 100 diseases that arise due to uncontrolled cellular growth.

The development of cancer occurs in three stages:  Initiation, Promotion, Progression'

Initiation
The development of precancerous cells.  The cell has been exposed to stress (such as oxidative stress) or to endogenous or exogenous carcinogens.  Precancerous cells form when the cell undergoes such exposure and fails to repair itself or die.  The cell forms DNA adducts - intermediates formed during phase I metabolism in the liver that may be carcinogenic and bind to DNA - which in turn distort the DNA, disrupting replication and/or translation.

Initiation alone is not enough for a cell to become cancerous.  However, the more precancerous cells that are initiated, the greater the risk for developing cancer.

Promotion
Stage 2 - the initiated cancer cell is further stimulated through cell signaling, which allows for cellular replication and growth leading to excess DNA damage that is beyond the capacity of the cell to repair the damage.
Also called cellular proliferation
Clusters of abnormal cells development, subsequently resulting in tumor formation,
Tumor types can be characterized by specific genetic lesions that develop during each step of the carcinogenesis pathway.
During the promotion stage, precancerous lesions can usually be detected (unlike during initiation)

Progression 
The cluster of abnormal cells may grow larger and/or translocate into other areas of the body (metastasize).