Introduction: Who Should Seek Diagnostic Testing

Neuroendocrine tumours often remain hidden for long periods because they may not cause noticeable problems until they affect an organ or produce excess hormones. Many people discover they have these tumours by accident during tests for unrelated health issues. However, you should consider seeking medical evaluation if you experience persistent symptoms that don’t improve over time.^[1]

Common warning signs include ongoing fatigue, unexplained stomach pain, persistent diarrhea, nausea and vomiting, shortness of breath, or coughing that sometimes includes blood. These symptoms can easily be mistaken for other less serious conditions, which is why they’re often overlooked or attributed to aging or stress. It’s important to remember that having these symptoms doesn’t necessarily mean you have cancer, but they warrant a conversation with your doctor, especially if they persist or worsen.^[2]

People with certain inherited conditions face a higher risk of developing neuroendocrine tumours and may benefit from regular monitoring. If you have Multiple Endocrine Neoplasia (MEN)—a rare genetic syndrome that causes tumors to form in various endocrine glands—your doctor may recommend periodic screening. The most common cancer syndrome associated with neuroendocrine tumours is Type 1 MEN (MEN1).^[2]

Even if you feel generally well, unexplained weight loss, a distended stomach, or difficulty eating more than a few bites of food could signal a problem worth investigating. Some patients later realize they had been ignoring or dismissing symptoms for months or even years before diagnosis. If something feels persistently wrong with your body, trust your instincts and seek medical advice.^[22]

Diagnostic Methods for Identifying Neuroendocrine Tumours

The diagnostic journey for neuroendocrine tumours typically begins with a thorough physical examination. Your healthcare provider will check for visible signs of cancer, such as swollen lymph nodes, and look for evidence that a tumour might be producing excess hormones. They will ask detailed questions about your symptoms, their duration, and any patterns you’ve noticed. This initial assessment helps guide which tests should follow.^[10]

Blood and Urine Tests

One of the first steps in diagnosing neuroendocrine tumours involves laboratory testing of blood and urine. Some neuroendocrine tumours produce excessive amounts of hormones, and these can be detected through specialized tests. Your doctor may order blood work to check for elevated hormone levels that could indicate a functioning tumour—one that actively releases hormones into your bloodstream.^[10]

Blood tests can also reveal indirect signs of a problem. For example, a patient might show anemia (low red blood cell count) or elevated liver enzymes, which can prompt further investigation. These findings don’t confirm neuroendocrine cancer on their own, but they serve as important clues that something needs closer examination.^[22]

Urine tests play a similar role, particularly in detecting certain hormone byproducts that functioning tumours release. The combination of blood and urine analysis helps paint a clearer picture of what might be happening inside your body and whether hormone production is abnormal.^[10]

Imaging Studies

Imaging tests create detailed pictures of the inside of your body, allowing doctors to see the location, size, and extent of neuroendocrine tumours. Several different imaging methods may be used, depending on where the tumour is suspected to be located and whether it may have spread to other areas.

Ultrasound uses sound waves to create images of organs and tissues. This non-invasive test is often used to examine the abdomen and can help identify tumours in the pancreas, liver, or other digestive organs. It’s painless and doesn’t involve radiation exposure.^[10]

Computerized tomography (CT) scans combine multiple X-ray images taken from different angles to create cross-sectional views of bones, blood vessels, and soft tissues. CT scans provide more detailed information than regular X-rays and can help determine the size of a tumour and whether it has spread to nearby lymph nodes or other organs.^[10]

Magnetic resonance imaging (MRI) uses powerful magnets and radio waves to produce detailed images of organs and tissues. MRI scans are particularly useful for examining soft tissues and can provide information that complements what CT scans reveal. Your doctor might order an MRI to get a better look at specific areas of concern.^[10]

Positron emission tomography (PET) scans represent one of the most important advances in neuroendocrine tumour diagnosis. These scans involve injecting a small amount of radioactive tracer into your vein. The tracer travels through your body and concentrates in areas where tumour cells are present. The PET scanner detects this radioactivity and creates detailed images showing exactly where active tumour cells are located.^[10]

The somatostatin receptor PET scan is particularly valuable because many neuroendocrine tumours have receptors for a chemical called somatostatin on their cell surface. The radioactive tracer used in this scan specifically targets these receptors, making it easier to find even small tumours that other imaging methods might miss. This precise detection helps doctors understand the full extent of the disease, including whether it has spread to distant organs.^[10]

Biopsy Procedures

A biopsy involves removing a small sample of tissue so it can be examined under a microscope in a laboratory. This is the only way to definitively confirm whether cancer cells are present and to identify the specific type of neuroendocrine tumour you have. The method used to collect the tissue sample depends on where the tumour is located in your body.^[10]

Some biopsies can be performed using a needle guided by imaging techniques such as ultrasound or CT scanning. The doctor inserts a thin needle through your skin to reach the tumour and withdraws a small tissue sample. Other situations may require an endoscopy—a procedure where a thin, flexible tube with a camera is inserted through a natural body opening to reach and sample the tumour. For tumours in the digestive tract, this might mean passing the endoscope through your mouth or rectum.^[10]

In certain cases, the biopsy may be obtained during surgery, especially if the tumour’s location makes other biopsy methods impractical or if surgery is planned as part of the treatment. Once the tissue sample reaches the laboratory, specialists examine the cells to confirm the diagnosis and gather detailed information about the tumour’s characteristics.^[10]

Laboratory Analysis of Tumour Tissue

After a biopsy is performed, laboratory tests analyze the tissue sample to determine critical information about your tumour. Pathologists examine how the cells look under a microscope and perform special tests to measure how quickly the tumour cells are dividing. This information helps classify your tumour into specific grades and types.^[6]

The differentiation of tumour cells refers to how much they resemble normal cells. Well-differentiated cells look more like healthy cells and typically grow more slowly, while poorly differentiated cells appear more abnormal and tend to grow faster. Your pathology report will describe the differentiation of your tumour cells.^[6]

The grading system for neuroendocrine tumours is based on how fast the cells are growing, measured by counting dividing cells (mitotic count) and using a marker called the Ki-67 index. Tumours are typically classified as Grade 1 (low-grade, slow-growing), Grade 2 (intermediate-grade), or Grade 3 (high-grade, fast-growing). This grading is crucial because it helps predict how the tumour might behave and guides treatment decisions.^[6]

The World Health Organization has established a classification system that categorizes neuroendocrine tumours into different groups based on their grade and other characteristics. Well-differentiated neuroendocrine tumours can be further divided into those with benign behavior and those with uncertain behavior. Well-differentiated neuroendocrine carcinomas show low-grade malignant behavior, while poorly differentiated neuroendocrine carcinomas are high-grade and include small cell and large cell types.^[6]

Diagnostic Testing for Clinical Trial Qualification

If you’re considering participating in a clinical trial, you’ll need to undergo specific diagnostic tests that serve as standard criteria for enrollment. Clinical trials have strict requirements to ensure that participants have the type and stage of disease being studied and are healthy enough to safely receive the experimental treatment.^[14]

Baseline diagnostic tests establish your cancer’s characteristics before any new treatment begins. These typically include comprehensive imaging studies to document the size, location, and extent of all detectable tumours. PET scans, CT scans, and MRI scans create a detailed map of your disease that researchers can compare to future scans to measure whether the treatment is working.^[14]

Blood tests are essential for clinical trial screening. Researchers need to verify that your liver, kidneys, and other organs are functioning adequately to handle the trial treatment. They also measure baseline hormone levels if your tumour is the functioning type. Complete blood counts check that you have sufficient red blood cells, white blood cells, and platelets. These tests must show that your overall health meets the trial’s safety requirements.^[10]

Tissue samples from your original biopsy may need to be retested or additional biopsies may be required. Many clinical trials, especially those testing targeted therapies, require confirmation that your tumour has specific molecular characteristics or receptors that the experimental treatment is designed to target. For example, trials testing treatments that work through somatostatin receptors need proof that your tumour cells actually have these receptors.^[14]

The grading and staging of your tumour must be precisely documented for clinical trial purposes. Researchers use standardized classification systems to group patients with similar disease characteristics. Your tumour grade (how fast cells are dividing), stage (how far the cancer has spread), and location all factor into determining trial eligibility. These details come from combining results from imaging studies, biopsies, and laboratory analyses.^[6]

Some trials require genetic testing of tumour tissue to look for specific mutations or molecular markers. This advanced testing examines the DNA of cancer cells to identify particular genetic changes that might make them respond to targeted treatments. While not all neuroendocrine tumour patients need genetic testing for standard care, it may be mandatory for certain clinical trials investigating precision medicine approaches.^[2]

Functional status assessments evaluate your ability to carry out daily activities. Clinical trial protocols often specify that participants must be well enough to care for themselves and spend a certain amount of time out of bed. This isn’t meant to exclude anyone unfairly, but rather to ensure that patients can safely tolerate the experimental treatment and that their health status doesn’t confound the study results.^[14]

Regular monitoring through repeated diagnostic tests is a fundamental part of clinical trial participation. Throughout the study, you’ll undergo periodic imaging, blood work, and other assessments at predetermined intervals. These repeated tests track how your tumours respond to treatment, detect any side effects early, and provide the data researchers need to evaluate whether the new therapy is effective.^[14]