Rarely, several generations of the same family will develop the same type of cancer at rates much higher than those that occur in the population overall. Often, the family members are passing on mutated genes that impart a higher than average risk for developing this particular cancer. By studying the genetic profiles of these affected families, researchers are learning which genes are involved in cancer's development. Kidney cancer families are a good example of this. When scientists discovered the gene changes involved in the inherited form of renal cancer, they were able to use this information to better detect and diagnose sporadic or randomly occurring new cases of this cancer type.

Only about 2 to 5 percent of cancers run in families this way.