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Since all our cells carry all of genes, most genetic tests are performed on a blood sample.  Before we indulge into the tests, it is important to understated the value of a test result, either positive or negative.

Negative test results:

We have to keep in mind that a negative test result does not mean that we would never develop the cancer for which the individual is tested for.  All it mean that they are not going to develop the familial or hereditary form of the cancer that is associated with the gene that they were tested for.  Those with negative tests results, at least have same chance of developing a specific cancer, as the whole population at large.  Women testing negative for breast cancer gene have same 1/10 chance of developing breast cancer .  The test results have to be interpreted very carefully and by qualified physicians.

Although we test for certain mutations, we can not test for all possible mutations.  Some of the mutations are not even know to us yet.  A familial cancer can be due to a mutant gene, that we don't have knowledge about.  As a result, a negative test in a family with positive history of hereditary cancers, does not exclude the possibility of an unknown mutant. Only a negative test result in a woman from a family with a know mutation is meaningful.

Positive test results:

The positive tests indicate to the presence of the mutant gene and the fact that the individual is at higher risk of developing a cancer.   Individual has to be counseled and potential interventions to be discussed.

Various available tests and the associated cancers:

·         BRCA1, for cancers of Breast, Colon, Ovaries, Prostate

·         BRCA2, for cancers of Breast, Colon, Ovaries, Prostate

·         p53, for cancers of Breast, Bone, Leukemia, Brain Tumor

·         APC, for Colon cancer

·         RET, for Medullary Thyroid cancer

·         VHL, Von Hipple Lindau

·         NF1, for Neurofibrosarcoma

·         RB1, for Retinoblastoma

·         BLM, for cancers of Colon, Esophageal, Tongue ,  Leukemia and Willms tumor

Cancer Genetic issues