Testing for GEP-NETs

There are many tests which can be used to help diagnose GEP-NETs. You might have a combination of different tests such as:

Blood tests:1,2

  • Chromogranin A and B
  • Full blood count (FBC)

Chromogranin is a substance produced by about 80-90% of GEP-NETs,3 so if it is found in the blood it is a good sign that there is a GEP-NET somewhere.

A full blood count will help doctors look for other possible causes of your symptoms, like anaemia or an infection.

Urine tests:2

  • 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.


  • 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.


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.

Further tests

There are also lots of tests to narrow down exactly what type of GEP-NET you have, which can include more scans and blood tests. Tests might also be done to see how much of particular hormone you have. This can help the lab work out where the tumour is, because we know that certain GEP-NETs produce certain hormones depending on where they are.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 draining and upsetting, 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 get.

Staging and grading

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


Different hospitals may use different systems for staging and grading, but one common staging system is known as TNM. This stands for:6

T – tumour: how big is the tumour?

N – node: are any lymph nodes affected?

M – metastasis: has the tumour metastasised i.e. spread to other parts of the body?

A number after each letter tells you and any other doctor treating you more information about the GEP-NET:

T1 – T4: T1 is the smallest, T4 is the largest

N0 or N1: N0 means no lymph nodes are affected, N1 means one or more lymph nodes are affected

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.


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 looking at the cells of the tumour.7

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

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 and what it is doing 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 and 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.

Next steps after diagnosis

Once the particular kind of NET you have has been diagnosed, staged and graded, your doctor(s) can put together a treatment plan for you. This might involve medications, surgery and/or other procedures like radiotherapy.

Vervolgstappen na diagnose

Zodra het specifieke type NET is gediagnosticeerd, gestadieerd en gegradeerd kan uw arts een behandelplan voor u opstellen. Het kan hierbij gaan om medicijnen, operaties en/of andere procedures zoals radiotherapie. Zie GEP-NET behandelen.


  1. NHS. Neuroendocrine tumours. Available at: Last accessed October 2020.
  2. Living with NETs. Tumor marker tests. Available at: Last accessed October 2020.
  3. Kizilgul M, Delibasi T. Review article: Gastroenteropancreatic neuroendocrine tumors (GEP-NETs).Transl Gastrointest Cancer 2015;4(1):39-56.
  4. Ramage JK, Ahmed A, Ardill J, et al. Guidelines for the management of gastroenteropancreatic neuroendocrine (including carcinoid) tumours (NETs). Gut 2012; 61:6–32.
  5. CRUK. Pancreatic NETs; stages. Available at: Last accessed September 2020.