The search started 20 years ago or so and was begun when it was noted that breast cancer can run in families. Some families have a very striking inheritance pattern where somebody's mother had breast cancer and their grandmother had breast cancer and two of their aunts had breast cancer and then another aunt had ovarian cancer—that's the kind of family history that suggests a cancer-causing gene mutation in the family.

This is called a cancer susceptibility syndrome. Another hallmark is having cancer at a very early age. So if you have a family history of a mother who got breast cancer at the age of 42, and a sister who got breast cancer at the age of 38, that's