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When cells become cancerous, they develop genetic changes that cause abnormal growth. These genetic changes—that occur after you are born and throughout your life—are known as somatic mutations. Experts can look at somatic mutations in cancer cells by testing a piece of the tumor. This process is known as genomic testing. Genomic testing can provide clues for treatment approaches such as targeted therapy.
Genomic testing to study mutations in cancer cells is different from genetic testing that is used to find germline mutations—inherited mutations in genes such as BRCA, PALB2, ATM, CHEK2 and others that are present at birth and significantly increase the risk of breast, ovarian and other cancers.
Somatic mutations found in tumors are different than germline mutations, which are inherited from either parent and are present in each cell. Unlike genomic testing, which is performed on tumor tissue, germline testing is usually performed on blood or saliva.
Tumor testing looks only for abnormalities in cancer cells. A tumor test may be done to determine if a tumor has certain features indicating that the cancer is more susceptible to treatment with a specific therapy.
Information provided by germline and tumor testing may overlap. For example, a person with cancer who has an inherited BRCA mutation will also have the same mutation in their tumor. Depending on the cancer type, both tumor and germline testing may be used to help select treatment options.