Genetic and genomic testing

Genetic testing and genomic testing may sound similar, but they are very different procedures. Genetics refers to the genes a person is born with that are inherited from past generations. Genetic tests may help determine whether a person has inherited gene mutations that may increase the risk of cancer. Genomics refers to the molecular composition of a tumor. Advanced genomic testing may help find gene mutations that may be driving a cancer’s behavior. Both types of tests may help you and your doctor make informed decisions about the types of treatment that should be recommended for your specific cancer.

Learn more about how genetics and genomics are different

Advanced genomic testing

In advanced genomic testing, a biopsy is taken of the patient’s tumor, cancer cells are isolated and extracted from the biopsy sample, and the cancer cells’ DNA is sequenced in the lab. Then, sophisticated equipment is used to scan the sequenced genetic profile for abnormalities that dictate how the tumor functions.

If identifiable abnormalities are found, they are analyzed to determine whether they match known mutations that may have responded to particular therapies or where evidence suggests there may be a potential treatment option not previously considered. If there’s a match, doctors may be able to use the results to suggest treatments that have been used in the past to target the same mutations.

Although conventional genomic testing is standard-of-care for some patients, advanced assessments are not recommended or available to all patients. Gene-mapping tests may be appropriate for patients with rare, unusual or hard-to-treat cancers, and for patients whose tumors did not respond adequately to conventional therapies.

Learn more about advanced genomic testing

Genetic testing

Genetic testing consists of a mouthwash or blood test. Analysis of the sample may determine a person’s likelihood of developing a certain type of cancer, whether a gene mutation contributed to an existing cancer diagnosis, and whether a person is at a greater risk of developing the same cancer again or developing another type of cancer.

A positive result on a genetic test does not always mean the person will develop cancer. It only means he or she carries one or more gene mutations. Similarly, a negative result on the test doesn’t mean a person will not develop cancer.

Learn more about genetic testing

Gene mutations

Gene mutations are permanent abnormal changes in the DNA of a gene. These mutations may increase the risk of developing cancer and other diseases. There are two types of gene mutations:

Acquired mutations occur when cells are damaged during replication, by viruses or by exposure to carcinogens, such as tobacco smoke or radiation.

Hereditary or germline mutations are passed down from generation to generation.

Not everyone with a gene mutation develops cancer, but either type of gene mutation may cause cells to grow out of control and form tumors. Acquired mutations are the most common causes of cancer. Hereditary mutations account for about 10 percent of all cancers.

Gene mutations that may play a role in the development of cancer include:


Mutations in the BRCA1 and BRCA2 (breast cancer 1 and breast cancer 2) genes may increase the risk of breast and/or ovarian cancer. BRCA mutations may be inherited and are associated with an increased risk of developing cancer. The BRCA gene test is typically recommended for people with a personal or family history of cancer, or for those with a specific type of breast cancer. The test generally isn’t performed on those with an average risk for breast or ovarian cancer.

Microsatellite instability and mismatch repair deficiency

Cancer is sometimes caused when the DNA in normal cells becomes damaged. But the body often fixes this damage before cancer forms, using mechanisms found in normal cells that look for repair flaws in DNA. One of those mechanisms is called mismatch repair, which corrects errors that occur when cells divide. When that function breaks down, the cells have what’s referred to as a mismatch repair deficiency (dMMR). Cells with dMMR can create an even more unstable cellular environment that causes microsatellites, or the repetitive stretches of DNA in a cell, to form mismatches, instead of exact duplicates of the DNA profile. This volatility is called microsatellite instability (MSI-H), and it sometimes causes cells to mutate and grow out of control, forming tumors. 

MSI-H and dMMR are found in a variety of cancers. For instance, MSI-H has been detected in 15 percent of all colorectal tumors, as well as in some uterine, bladder, breast, prostate and thyroid cancers. The defect has also been found in 90 percent of colorectal cancer patients who also have Lynch syndrome, a genetic condition that elevates the risk for some cancers. Not all cells with dMMR develop MSI-H. And, in rare cases, MSI-H can occur in cells without dMMR. Immunotherapy drugs called checkpoint inhibitors have been approved to treat cancers with dMMR or MSI-H.


Programmed cell death receptor 1, or PD-1, is a protein receptor found on T-cells, which are immune cells that protect the body from disease and infections. PD-1 is called a checkpoint protein because it seeks out cells and checks to see if they are harmful. When the PD-1 on an immune cell interacts with PD-L1 on another cell, it shuts down an immune response. Some cancer cells may have many PD-L1 receptors, allowing them to disguise themselves as healthy cells when “checked” by the immune system. Checkpoint inhibitors are designed to block the interaction of PD-1 and PD-L1 receptors and allow the immune system to better recognize cancer cells and attack them. These drugs have been approved to treat a variety of cancers, including melanoma, lung and bladder cancers.

Other gene mutations that may be found in cancer include:

Genetic mutation Associated cancer Test Comments
ALK gene Lung cancer, non-Hodgkin lymphoma Tumor biopsy Tests may help determine treatment options and response.
Philadelphia chromosome Leukemia Blood or bone marrow test Tests may help diagnose cancer and determine treatment options.
BRAF V600 Melanoma, colorectal Tumor biopsy Tests may help determine treatment options.
C-kit/CD117 Gastrointestinal stromal tumor, melanoma Tumor biopsy Tests may help diagnose cancer and determine treatment options.
Estrogen receptor (ER) and progesterone receptor (PR) Breast cancer Tumor biopsy Tests may help determine treatment options.
KRAS Colorectal cancer, lung cancer Tumor biopsy Tests may help determine treatment options.