Genetic testing: Testing a tissue sample of a family member

If there’s a suspicion that the cases of cancer in your family are down to an inherited gene fault like BRCA1/2 or Lynch syndrome, the best way to find out is to test a person who has a diagnosis of cancer. Sometimes, unfortunately, this person has already passed away before being able to have this testing. 

However, it may still possible to find out if that person carried a faulty gene by testing a tumour or blood sample that was previously saved and stored. So how do you access this testing?

Why would there be a tissue sample saved somewhere?

When a person has a cancer diagnosis, often a biopsy or surgery to remove the cancer is performed. The tissue samples taken from their tumour are used for investigations such as identifying the type of cancer and how best to treat it. Sometimes, extra blood samples are taken in order to perform additional tests at a later date. These samples can be stored for many years in case further testing is needed, so even if your relative passed away some time ago, it may be possible that there is a sample that can be tested.

However, if your relative had their cancer treatment in a different country, your genetics team in the UK will not be able to access the tissue sample to test it.

How does permission work?

If the person is still alive, they must give their consent to have their tissue sample tested for genetic faults. If the person has passed away, their next of kin or certain relatives can give permission on their behalf.

Is there a reason why this testing would fail?

Sometimes there is not enough of a sample left, or the sample is not of good enough quality to perform testing. In this case, your genetics team will be able to advise you on the next steps for your family.

How long do results take?

Obtaining the sample and testing it can take several months , as it is complex. Your genetics team can give you an idea of current time frames and how that may impact your own decisions.

What if there is no tissue sample saved?

If there is no tumour or blood sample available and the family member has passed away, your genetics team will be able to explain to you whether or not you are eligible for genetic testing yourself based on your family history of cancer.

How do I find out more?

You would need to be referred to your local clinical genetics team to find out whether your family history indicates there may be a hereditary cause for the cancer in your family. They can explain to you whether tissue testing is the most appropriate option for you, and arrange the process. You can ask your GP if you’re eligible for a referral to your local genetics clinic.

What do the results mean?

If the results show that your relative carried a high-risk faulty gene, such as BRCA1/2 or Lynch syndrome, and they are a close blood relative, then you would be able to access testing yourself. If they are more distant relatives, it may be that closer family members in your family tree need to be tested first. Speak to your GP (or genetics team if you are already in touch) to find out more.

If the results show that your relative did not carry a faulty gene, then their cancer was not caused by one of these faulty genes, and you cannot have inherited one of these faulty genes from them. You should note, though, that this does not guarantee you have a low risk, as faulty genes that increase cancer risk can be inherited from both sides of the family. If you are still concerned about inherited risk, it is worth researching as much as you can about your family history and drawing out your family tree before you speak to your GP.

With thanks to Pooja Dasani, Genetic Counselling Lead at North Thames GMSA and Principal Genetic Counsellor based at Great Ormond Street Hospital.