What’s changed in 20 years of testing for familial cancer?

Twenty years ago, when BRCA1, BRCA2 and a number of other cancer predisposition genes were identified, the cause of most cancers was considered ‘hereditary' or ‘sporadic'.

The hereditary group was thought to be due to a small number of genes associated with a very high risk of cancer. When BRCA1 and BRCA2 failed to account for a large proportion of families with multiple cases of breast cancer, the discovery of BRCA3 was thought to be imminent.

Have we explained the familial basis of common cancers?
For