Abstract
Oncological genetics is defined as a branch of clinical cancer research dealing with the identification, description, analysis, and prevention of those human neoplasias and their related/associated syndromes in which a vertical (hereditary) transmission is assumed. The present clinical basis of this field is constituted by the 240 inherited preneoplasias and neoplasias that have been detected so far. The main hypothesis in oncological genetics might be the existence of an inherited cancer proneness phenotype (CPP), in whose determination the processes involved in the activation of cellular proto-oncogenes would presumably play a role. It is conjectured that CPP is a quantitative (random) variable with extreme values. Such indicators can be identified in small populations having a structure (i.e., tree) so that the collection of comprehensive pedigree data is indispensable.