Cancer is a multifactorial disease due to the combined effect of genetic and environmental factors. A small proportion, it is estimated that about 5% of all tumors have a hereditary character. Hereditary cancers are the result of germline mutations in particular genes that increase susceptibility the risk of cancer. This susceptibility is transmitted among family members according to different patterns of inheritance. Susceptibility to cancer is inherited, which does not imply the certainty of developing it in all cases. In recent years it has been identified about 50 genes involved in as many hereditary predisposition cancer syndromes, and many techniques have been developed for their characterization or their mutations.