Hereditary cancers are common in clinical oncology 5-10% of all diagnosed neoplasms are estimed to be hereditary cancer.Therefore, careful study of the family history, as well as knowledge of the basic principles of genetics is required to address this type of patient.The purpose of this article is to offer basic genetics concepts as a useful tool in oncology clinical practice with practical examples, as well as to justify why a genetics specialist should be part of the multidisciplinary team in patients with a suspected hereditary oncologic condition.(creativecommons.