Familial cancer and cancer families.

From this brief review is should be evident that the hereditary varieties of common cancers are characterized by a high degree of genetic heterogeneity. The specific types of hereditary cancers can be identified by focusing on the histologic types and sites of involvement, not only of the primary neoplasm, but also of associated neoplasms and associated conditions or stigmata, as well as by focusing on the age of the patient at the time of diagnosis, tumor localization and frequency, and the mode of inheritance. Identification of specific types of hereditary cancers has important utility as a means of isolating homogeneous groups of patients and unaffected relatives for studies aimed at elucidating the mechanisms of carcinogenesis.