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Hormonal and Rare Conditions Neuroendocrine Tumors Testing
Testing
Diagnosing GEP-NETs

Testing

There are many tests which can be used to help diagnose GEP-NETs, and your doctor may order a combination of different tests.

These can include:

Four text boxes labelled blood tests, urine tests, scans, biopsy. Blood tests: Chromogranin A, full blood count (FBC), serotonin, 5-HIAA. Chromogranin is produced by 80-90% of GEP-NETS, making its presence in blood a strong indicator of a GEP-NET. A full blood count will help doctors look for other possible causes of your symptoms, like anaemia or an infection. (References 1-4). Urine test: 5-HIAA. 5-HIAA is a substance produced by some GEP-NETs, so finding it in urine can help narrow down the cause of any symptoms. (References 1,2,4). Scans: Ultrasound, CT (computerised tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), nuclear medicine where you’re given a slightly radioactive tracer substance which shows up on scans. Various scans may be used to get a visual picture of what’s going on, and can help find where in the body the GEP-NETs are. (References 1,4). Biopsy: This is when a small amount of tissue is taken from the tumour to be examined in the lab, to check for signs of tumours or abnormal cells. (References 1,4).

Further tests

To narrow down what type of GEP-NET you have, further tests can be used, which can include more scans and blood tests. Tests might also be done to see how much of a particular hormone you have. This is because certain GEP-NETs produce certain hormones depending on where they are in the body.5

The testing process for GEP-NETs can be long and complicated, with a lot of time spent going to hospitals. This is because diagnosing GEP-NETs is almost like a detective following leads, checking out every possibility and eliminating suspects one by one. Although this can be very emotionally draining, try to remember that every test, positive or negative, takes you one step closer to getting the right diagnosis. It can help to bring someone with you to appointments – they can offer emotional support, and can also help you remember more of the information you receive.

Once you have been diagnosed with a GEP-NET, the next step is to find out more about your particular tumour. This involves staging and grading it:4

  • Staging describes what the GEP-NET is like, such as its size, where it is and whether or not it has already spread.
  • Grading describes what the GEP-NET is doing in terms of how fast or slow it is growing and whether or not it is likely to spread further.

Staging

Different hospitals may use different systems for staging and grading, but one common staging system is known as TNM. A number after each letter tells you and any other doctor treating you more information about the GEP-NET:

An infographic explaining the TMN acronym. T: Tumour - how big is the tumour? T1-T4. T1 is the smallest, T4 is the largest. N: Node - are any lymph nodes affected? N0 or N1. N0 means no lymph nodes are affected, N1 means one or more lymph nodes are affected. M - Metastasis: has the tumour metastasised i.e. spread to other parts of the body? M0 or M1. M0 means the tumour has not spread, M1 means it has spread.

You might also see GEP-NETs described as Stage I, Stage II, Stage III, or Stage IV. This is another system like TNM, and it describes the same kind of things, like size, place, and metastasis (spread).

  • Stage I is the earliest stage, when the tumour is small and hasn’t spread.
  • Stage IV is the latest stage, when the tumour has spread to other parts of the body.

Grading

It’s important to know what the tumour is doing, so we can work out whether or not it is likely to spread to other parts of the body, and if so, how quickly. This is done by examining the cells of the tumour.6

G1 – grade 1: the cells are mostly acting like normal, healthy cells, so the tumour isn’t growing very quickly

G2 – grade 2: the cells are slightly abnormal; the tumour is growing quite quickly

G3 – grade 3: the cells are very abnormal; the tumour is growing fast

A photo of a high grade (grade 3), intermediate grade (grade 2), and low grade (grade 1) tumour cells.

Going through all these tests and waiting to hear about the stage or grade of a tumour can be very difficult and stressful. But it’s essential for your medical team to know as much as possible about your GEP-NET so that they can work out what treatments are needed. There are a lot of treatment options for GEP-NETs, and it all depends on where the tumour is, what stage and grade it is, as well as how fit and well you are in general.1 What works in some cases doesn’t work in others, and the more the team know, the better they can decide what to do next.

References

  1. CRUK. Tests to diagnose neuroendocrine cancer. Available at: https://www.cancerresearchuk.org/about-cancer/neuroendocrine-tumours-nets/getting-diagnosed/tests-diagnose. Last accessed April 2025.
  2. Living with NETs. Tumor marker tests. Available at: https://www.livingwithnets.com/en-us/tumor-marker-tests/. Last accessed April 2025.
  3. Díez M, Teulé A, Salazar R. Gastroenteropancreatic neuroendocrine tumors: diagnosis and treatment. Ann Gastroenterol. 2013;26(1):29-36.
  4. Macmillan. Diagnosis of NETs. Available at: https://www.macmillan.org.uk/cancer-information-and-support/neuroendocrine-tumours-nets#diagnosis_of_neuroendocrine_tumours_nets. Last accessed April 2025.
  5. Ramage JK, Ahmed A, Ardill J, et al. Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours (NETs). Gut 2012; 61:6–32.
  6. CRUK. Grades and stages of neuroendocrine cancer. Available at: https://www.cancerresearchuk.org/about-cancer/neuroendocrine-tumours-nets/grades-stages. Last accessed April 2025.