Clinical/genetic features in hereditary breast cancer.

Patients from hereditary breast cancer-prone (HBC) families provide one of the most powerful and potentially cost effective models for cancer prevention and control. Paradoxically, this opportunity is often missed in the clinical practice setting due, in part, to inattention to the family history and/or lack of knowledge about breast cancer genetics. We describe the family study process, wherein documentation of genealogy, medical, and cancer history through pathology verification is attained, often on extended families. The findings of such studies are illustrated by description of nine breast cancer-prone families. These families illustrate several important clinical/genetic features such as age of cancer onset, bilaterality and/or multiple primary cancer occurrences, incomplete gene penetrance, and the identification of putative obligate gene carriers. Interpretation of HBC pedigrees is dependent upon the understanding of these issues, which in turn may enable the physician to more readily identify those individuals who might benefit from highly targeted breast cancer control measures.