The cancer formation, in general of – slowly, being able to take some years so that a cancerous cell originates a detectable tumor. This process passes for some periods of training before arriving at the tumor: Period of training of initiation: It is the first period of training of carcinognese. In it the cells suffer the effect from a carcinognico agent (oncoiniciador agent) that it provokes modifications in some of its genes. In this phase the cells meet modified genetically, however not yet it is possible if to detect a tumor clinically (ALMEIDA et al., 2005). Period of training of promotion: The cells genetically modified suffer the effect from the classified cancergenos agents as oncopromotores. The initiated cell is transformed into malignant cell, of slow and gradual form.

So that this transformation occurs, it is necessary a long one and continued contact with the promotional cancergeno agent. The suspension of the contact many times interrupts the process in this period of training (ALMEIDA et al., 2005). Period of training of progression: It is the third and last period of training and is characterized for the uncontrolled multiplication, being a irreversible process. The cancer already is installed, evolving until the sprouting of the first clinical manifestations of the illness (ALMEIDA et al., 2005).