Short answer
Tumor genomic testing, sometimes called biomarker testing or somatic testing, looks for changes in the cancer itself to help choose treatment or classify the cancer. Inherited genetic testing, also called germline testing, looks for variants present from birth that can affect cancer risk for the person and their relatives. The same gene can matter in both settings, but the question being asked is different.
Key differences
| Question | Tumor genomic testing | Inherited genetic testing |
|---|---|---|
| What sample is tested? | Tumor tissue, or sometimes tumor DNA from blood. | Blood, saliva, or another non-tumor sample. |
| What is the goal? | Guide treatment, trial matching, or tumor classification. | Estimate inherited cancer risk and guide prevention or family testing. |
| What kinds of changes are found? | Usually somatic changes acquired by the cancer. | Germline variants present in most cells from birth. |
| Who else is affected? | Usually the cancer treatment team. | Biological relatives may need testing or counseling too. |
When both matter
CDC and NCI both note that a tumor result can raise suspicion for inherited cancer risk, but that does not prove it. For example, an abnormal tumor result in a mismatch-repair gene can trigger germline follow-up for Lynch syndrome. A BRCA-type finding in tumor testing can also lead to a separate inherited-risk conversation.
That is why the order of testing matters. If you are asking whether a cancer is driving a treatment decision, tumor testing may be the right first step. If you are asking whether a family could carry an inherited cancer syndrome, germline testing and counseling matter more.
What tumor-only results cannot tell you
Tumor-only testing can be useful, but it cannot always tell whether a finding is truly inherited, limited to the cancer, or influenced by how the sample was collected and analyzed. A separate germline test may be needed if the result could change family screening or inherited-risk counseling. A negative tumor result also does not rule out inherited risk if the family history still looks suspicious.
When counseling helps sort the result
Counseling is useful when a tumor report looks genetic but may actually be somatic, because the next step might be germline testing, tumor review, or neither. It also helps families understand why a cancer treatment result does not automatically equal inherited risk.
Questions to ask
- Is this result from the tumor, from inherited DNA, or both?
- Does the finding change treatment, surveillance, or trial options?
- Should I have confirmatory germline testing after this tumor result?
- Could family members need counseling or testing?
- Would a genetic counselor help interpret the report?
FAQ
What is the main difference between tumor and inherited genetic testing?
Tumor testing looks for changes in the cancer itself. Inherited testing looks for variants present from birth that may affect the person and their relatives.
Can a tumor finding mean the change is inherited?
Sometimes, but not always. A tumor finding can suggest inherited risk, but a separate germline test is often needed to confirm it.
Why is biomarker testing done in cancer care?
Biomarker testing can help choose treatment, match a clinical trial, or better classify the cancer.
When should germline testing be considered after a tumor result?
When the tumor result involves a gene tied to inherited risk, or when personal or family history makes inherited cancer risk plausible.
Does a negative germline test rule out all inherited risk?
No. It can still leave family-history risk, testing-panel gaps, or a variant not included in the assay.
Who should help interpret the result?
An oncologist, genetic counselor, or both are often useful when the result could change treatment, surveillance, or family testing.
Does a tumor-only result rule out inherited risk?
No. A tumor-only result can be a clue, but it does not replace germline testing when the family history or gene pattern suggests inherited risk.
Related guides: hereditary cancer genetic testing, whole genome sequencing reports, FDA-authorized genetic tests, and when to use a genetic counselor.