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Which tests are used in helping to diagnose NET cancers?

There are a number of different tests and scans which may be used to detect a NET cancer. Some of these tests work by looking for hormonal changes triggered by the cancerous cells, while others look for the tumor itself.

NB: There is no standard group of tests – each patient may need to undergo a different combination of tests. If you have any questions about these tests, please confer with your medical team.

 

Biopsy

This involves taking a piece of tissue from the suspect tumor and having it analyzed in the laboratory by a specialist called a histopathologist.

Specifically, in clinical medicine, histopathology refers to the examination of a biopsy or surgical specimen by a pathologist, after the specimen has been processed and histological sections have been placed onto glass slides.

The pathologist may review the biopsy sample and give the tumor a proliferative index, i.e. a measure of the number of cells in the tumor that are dividing (proliferating). A proliferation index of less than 2% means that the tumor is very slow growing, while a value above 10% suggests faster growth. The test for determining a proliferation index is called Ki67 or MIB1.

Being able to look at the tumor under the microscope can be the only way to determine exactly what type of NET cancer it is.

 

Blood Tests

diag blod1

The patient may be asked to have a fasting gut hormone blood test, and blood will also be collected for a range of other tests. Doctors will be looking for certain NET markers, particularly chromogranin A and B, pancreatic polypeptides, insulin and gastrin, glucagon, neurotensin, VIP (vaso-intestinal peptide) and for evidence of a rise in certain peptides and hormones in the blood, as well as checking how well the kidneys and liver are functioning. If the results of these tests suggest the presence of a NET, further imaging tests should be carried out.

Other biochemical tests

  • A summary of other biochemical tests is listed below:
  • Full blood count
  • Kidney function tests (urea and electrolytes)
  • Liver function tests
  • Thyroid function tests
  • Pituitary hormone screen, e.g. adrenocorticotropic hormone (ACTH), prolactin, growth hormones and cortisol
  • Serum calcium, parathyroid hormone levels (in all pancreatic NET patients, as a simple screening test for MEN-1 syndrome)

 

Urine Tests

5-HIAA (hydroxyindoleacetic acid) is a substance that is naturally passed out by the body. Normally, only small amounts are present in the urine. Elevated levels in a urine sample may indicate a NET, although further tests are required to confirm the diagnosis. This test can also be negative even if a person has a NET cancer, and further testing is essential.

The patient will be asked to avoid certain foods prior to and during the 24-hour test, including chocolate, olives, bananas, pineapple and its juice, all tomato products, plums, eggplant, avocado, kiwi fruit, nuts, especially walnuts, tea, coffee and alcohol. They will also be asked to avoid certain medications two days prior to the test, including certain cough, cold and flu medicines; hypertension medications; muscle relaxants; Valium and Flexeril; and MAO inhibitors, including natural herbs purchased in health food stores that produce the same effect. This is because they contain substances that might artificially raise serotonin levels and give a false test result.

 

Endoscopy

In this test, a flexible camera, called an endoscope, is used to examine the digestive tract. The tube can be inserted down the back of the throat (gastroscopy) or via the rectum (colonoscopy). In both cases the patient will be offered sedation. If abnormal-looking tissues are found during this procedure, a sample can be collected and examined under a microscope. A tissue biopsy like this can be the only definitive test for a NET cancer.

 

Endoscopic Ultrasound

In this test, an ultrasound is first used to locate suspect areas, before the endoscopy is performed.

 

Wireless Capsule Endoscopy

This is a noninvasive procedure in which a small capsule containing a video camera is swallowed by the patient. As it passes through the gastrointestinal tract it records the mucosa of the small bowel. These images are transmitted by a radiofrequency signal to a data recorder attached to the patient’s waist. After approximately 8 hours the capsule is excreted and the recorded data is downloaded to a computer where it can be viewed, edited and recorded.

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