Genetic Testing – Understanding the Role of Germline versus Tumor Testing

01 Oct 2020 by Pink Hope Team
Genetic Testing – Understanding the Role of Germline versus Tumor Testing

With the personalisation of treatment through advances in precision medicine and, genetic testing, we are seeing exciting changes to the care of many individuals diagnosed with hereditary cancers.

With this in mind, we have pulled together the below outline of exactly what tumor and germline testing is, to keep you educated, informed and empowered when it comes to your own healthcare journey.

Genes and cancer

One way to explain what genes are and how they relate to cancer, says Genetic Health Queensland Staff Specialist Dr Helen Mar Fan, is to think of them as a set of instructions which tell our cells how to grow, develop and function. As we live, she says, lifestyle and environmental factors can cause faults (mutations) in our genes.

“Mutations which occur through the process of living are called somatic mutations. Over time, if enough mutations develop, a cancer may form,” Dr Mar Fan explains. “Sometimes, testing of a person’s cancer (‘tumour testing’) is arranged to identify any somatic mutations that may assist with treatment decisions.”

These somatic mutations are only in the cells of the cancer, Dr Mar Fan advises and cannot be passed from parent to child (cannot be inherited).

Hereditary mutations

By contrast, instead of increasing mutations growing over time, a person can be born with a mutation that increases their chance of developing cancer. These mutations are called germline mutations and are present in every cell of the body.

“Germline mutations can be passed from parent to child, and in families where an inherited predisposition to cancer is suspected, a genetic blood test (‘germline testing’) may be recommended.” Dr Mar Fan explains.

Inherited genetic mutations play a significant role in about 5 to 10 percent of all cancers, and so if genetic testing identifies a germline mutation, Dr Mar Fan says testing can be offered to other family members to clarify their chance of developing cancer.

Which test do I need?

There are three tests that help to identify cancer mutations, they are:

Genetic testing is used in both germline and tumour testing, with each providing specific data which is used to guide treatment plans and to identify potential future risks for a patient and their family members.

Tumor testing can predict how aggressively a cancer may behave and whether it’s likely to recur, whilst also providing information that can inform cancer treatment options and the opportunity for participation in clinical trials. Tumor testing looks only for abnormalities in cancer cells and is carried out on tumor tissue.

Germline testing provides a precise risk evaluation to support preventative screening, medical and surgical options that reduce risk.  Germline testing is carried out on cells that do not have cancer and is usually performed on blood, saliva or skin cells.

Overlapping results

It’s important to note that information that is gained from both germline and tumour testing may in fact overlap. For example, a woman with breast cancer who has an inherited the BRCA mutation will also have the same mutation in her tumor.

At times, says Dr Mar Fan, depending on the specific cancer, both tumor and germline testing may be used to help determine treatment options.

“If a somatic mutation is identified, patients may be concerned for their relatives,” she says. “However, it is important to remember that most somatic mutations do not have implications for other family members. If a patient’s treating team suspects that a germline mutation could be present, they may offer to arrange germline testing, or referral to a genetics or family cancer service.”

Genetic Counsellors play an important role in helping individuals and families learn how gene mutations are inherited and who in the family may be at risk. They also provide emotional support and counselling throughout the genetic testing process.

You can access the Ask Our Genetic Counsellor service here, this service provided by Pink Hope allows you to submit questions relating to your risk of breast and ovarian cancer to our qualified Genetic Counsellor. 


Thank you for visiting Pink Hope! Keep reading our blog for more articles about breast and ovarian cancer, and find out how to volunteer, support or donate to Pink Hope in the future. Pink Hope is a preventative health hub providing essential tools for assessing, managing and reducing your risk of breast and ovarian cancer, as well as providing personalised support for at-risk women.

This article was sponsored by Astra Zeneca and developed independently by the team at Pink Hope in consultation with medical experts. 


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