Blood tests currently offer limited insight into cancer risk, as most cancers result from somatic, not germline, mutations, with exceptions like BRCA and Lynch syndromes.

“so probably one thing i always point out to patients here as well is they say i had a genetic test you know i had a 23andme test doesn't that tell me about my risk of cancer given that it's a genetic disease and the answer is basically no it does not the genetic tests that people get when they do you know genetic sequencing are what are called germline genes so these are the genes that you inherited most cancers do not arise from inherited genes it's on the order of five percent of cancers that come from inherited forms of cancer meaning our inherited forms of cancer the majority of them at least 95 percent result from somatic mutations so mutations that occur to your genes and they're not that necessarily the genes you pass on”