If leukemia is genetic how is it not hereditary?

Mutation: Leukemia, like most cancers, is felt to be secondary to mutations to critical control genes that occur after birth; if the mutation does not happen, there is no leukemia. That being said, some people may have versions of genes that are easier or harder to mutate to an uncontrolled version, but it's hard to prove direct causation. One notable exception is the brca gene mutations in breast cancer.

See below. : The genetics of the leukemia are acquired by the leukemia cells. This creates genetic abnormalities in the leukemia cells, but you are not born with these genetic abnormalities. Neither the genetic abnormality of the leukemia nor the predisposition to acquire this disease is hereditary that we know of.