Information provided by tumor genomic profiling and germline genetic testing may overlap. For example, a person with cancer who has a germline MSH2 mutation will also have the same mutation in their tumor. Somatic testing labs may or may not report likely germline variants. In comparison, a germline genetic test may pick up somatic mutations that have sloughed off the tumor and are circulating in the blood (ctDNA). Traditionally somatic mutations that are identified in the blood are seen at very low levels.

You cannot assume that a tumor profile test will detect germline mutations, and most germline tests will not report likely somatic mutations. Depending on the cancer type, both tumor and germline testing may be used to help select treatment options.

*Importantly, germline genetic testing may be needed as a follow up to tumor genomic profiling. You cannot rule out Lynch syndrome with tumor genomic profiling alone. Germline genetic testing is always needed to confirm Lynch syndrome.