Hereditary syndromes cause approximately 5 to 10% of overall cancer cases. Cancer related with genetic syndromes are found elsewhere, including stomach, breast, colorectum, ovary, brain and so on. Because hereditary cancers are due to germline mutations, these patients have unique clinical features distinct from sporadic cancer. Generally these features include (i) early age-of onset of cancer, (ii) frequent association with synchronous or metachronous tumors, (iii) frequent bilateral involvement in paired organs (iv) frequent association with other site tumors or characteristic clinical manifestation specific to each genetic syndrome. Due to these differences, the management strategy for patients with hereditary cancer is quite different from that for sporadic cancer. Additionally, there are important screening and surveillance implications for family members. Genetic counselling is prerequisite to these families for risk assessment by pedigree analysis, and guidance to clinical or genetic testing. The genes responsible for these syndromes has recently identified, as a result, genetic testing has become important determining factor in clinical decisions.