Key diagnostic procedures for NET explained
Biopsy
A neuroendocrine tumor biopsy is a diagnostic test where a small piece of tissue from the suspected tumor is removed. There are different types of biopsies, and you and your doctor may discuss which is most suitable for you. For example, the biopsy might be done using endoscopy, or you might need surgery. The removed tissue is analyzed in a laboratory. Using immunohistochemistry, a pathologist tests the tumor tissue for specific neuroendocrine tumor biomarkers, such as chromogranin A. This type of test uses antibodies bound to a dye, which helps to reveal certain structures when it is looked at under a microscope. From this, the pathologist can get information about the tumor cells. This helps to accurately diagnose NET.
Understanding your neuroendocrine tumor pathology report is important. Your doctor will use this to develop a personalized treatment plan for you, so it is helpful to be familiar with the information.
Endoscopy
Endoscopy allows doctors to remove small pieces of suspicious tissue for analysis at the laboratory. It is usually done under sedation. Depending on the location and type of tumor, your doctor may use one of the following procedures:
Gastroscopy or colonoscopy: Uses a thin, flexible fiber-optic tube called an endoscope. This is inserted down the esophagus and into the stomach (gastroscopy), or into the colon via the rectum (colonoscopy). This allows the doctor to examine different parts of your digestive tract
Bronchoscopy: Uses a narrow, flexible fiber-optic tube called a bronchoscope. This is inserted down the throat and into the airway to see the trachea and lungs
Endoscopic ultrasound: The doctor looks at the digestive tract and surrounding organs (like the pancreas) with a flexible camera that can also perform ultrasound. This can help pick up small tumors that might not be visible on other scans
Blood tests
When diagnosing neuroendocrine cancer, your doctor may order blood tests to check for increased levels of neuroendocrine tumor biomarkers in your blood. This includes specific proteins and hormones that may help reveal the NET type. These diagnostic tests may look at your kidney function (urea and electrolytes), liver function, thyroid function, pituitary hormones (such as prolactin or growth hormones), serum calcium, chromogranin A, or plasma metanephrines, among others.
Urine tests
Urine testing is common in neuroendocrine tumor diagnosis. Many functional NETs produce high levels of serotonin. This is broken down in your body into a compound called 5-HIAA, which is then excreted in urine. To perform a HIAA urine test, you may be asked to collect urine samples over a 24-hour period, as serotonin levels can vary throughout the day. In preparation for this, you may be asked to avoid certain medicines, and some foods rich in serotonin (such as chocolate, olives, and bananas) for 3 to 7 days before the test.
NET imaging techniques
Radiological imaging plays a key role in neuroendocrine tumor diagnosis and monitoring. These diagnostic tests help identify the tumor’s location, size, and possible spread.
Computed tomography (CT) scans provide a 3D picture of the inside your body. A series of cross-sectional images are taken with a specialized X-ray machine. The scan itself does not take long (approximately 10 to 30 minutes). Depending on the scan type, you may be asked to drink a contrast solution or receive a contrast dye injection. This helps make specific tissues more visible and produces better images of any tumors or other abnormalities.
Magnetic resonance imaging (MRI) scans use magnetic fields to detect small tumors and metastases. They typically take longer than CT scans (approximately 30 to 90 minutes) and can feel noisier (you may be given earplugs). MRI scans take place in a special machine that can make some people feel claustrophobic. If you suffer from claustrophobia or have other concerns, talk to your doctor about receiving sedation to help you feel more comfortable. You should not have an MRI if you have any metal parts in your body such as a pacemaker, bone, or tooth implant. Make sure you talk to your doctor to find out if an MRI is right for you.
Ultrasound scans use high-frequency sound waves to produce pictures of the inside of the body. They are non-invasive, meaning the test is done entirely outside the body without anything entering it, and the images are captured in ‘real-time’. Ultrasound scans can show the structure and movement of your body’s internal organs, and even your blood flowing through blood vessels.
Nuclear imaging
Nuclear imaging techniques, also known as functional scans, are a valuable tool in neuroendocrine tumor diagnosis. A small amount of a radioactive agent is injected into your bloodstream. This binds to receptors on the tumor surface and releases a radioactive signal, which can be detected by a scanning device. Different nuclear imaging techniques are specific to certain types of NETs and their metastases.
Positron emission tomography (PET) is often combined with CT scans to provide more detailed images. This is known as a PET/CT scan. Some examples may include:
Gallium-68 or Copper-64 PET scans may be used in people with NETs that express somatostatin receptors. This scan can detect tumors anywhere in the body that are difficult to detect using MRI or CT scans alone.
18F-FDG PET scans detect cells that rapidly reduce the glucose in your body, which is a feature of many types of cancer. Some NETs, particularly aggressive and faster-growing ones, may be detected in this scan.
Octreotide scans, also known as somatostatin receptor scintigraphy (SRS), are used to detect NETs expressing somatostatin receptors. This scan uses a drug called octreotide with a radioactive tracer attached to it. This is injected into a vein, travels through your bloodstream, and binds to tumor cells. A special camera then captures images of areas where the tracer has collected, helping to locate tumors in the body.
