Carcinoid or neuroendocrine tumors (NETs) are neoplasms, which form among cells within the endocrine and nervous systems. These cells are located virtually throughout the body such as the lungs, stomach, small intestine, pancreas, appendix and rectum. Some of these tumors secrete hormones which result in symptoms such as flushing, diarrhea and wheezing. This set of symptoms is called carcinoid syndrome. Many, however, do not produce hormones. Due to this, NETs are often detected unexpectedly during routine testing such as colonoscopy or amidst work-up for another disease.
Depending on their grade, NETs may be slow-growing or aggressive. Approximately 67% of NETs occur in the gastrointestinal system and the pancreas. Twenty-seven percent occur in the lungs, and 6% occur in other parts of the body. The incidence of NETs worldwide has risen in the past 40 years and continues to rise.
Diagnosis of neuroendocrine tumors is determined by blood work, imaging and pathology.
Common laboratory tests monitored at our center are Chromogranin A (CgA), 5HIAA, gastrin and serotonin. Pancreastatin may also be monitored is some situations. These are drawn based on the tumor’s location. Elevation of these may indicate presence of NET. However, results may be influenced by medication or other diseases. For instance, persons who take proton pump inhibitors (PPIs) such as omeprazole or pantoprazole may have increased levels of CgA and gastrin. Liver or kidney disorders may also increase CgA.
Computed Tomography scan (CT) and Magnetic Resonance Imaging (MRI) can localize neuroendocrine tumors. NETs are typically hypervascular, which means they have increased blood supply. As a result, they tend to have increased enhancement—or light up more– in these imaging tests.
Gallium 68 PET (Positron Emission Tomography)/CT scan with Dotatate is a study specific for neuroendocrine tumors. Compared to normal tissues, NETs have a greater number of markers called somatostatin receptors on their surface. The 68 Ga scan takes advantage of this unique feature. The radiation given with 68 Ga scan is bound with a protein that is drawn to these markers. 68 Ga scan has been used to rule out metastases or detect tumors not found in CT or MRI.
Pathology is obtained from a biopsy or a surgical resection. The specimen is analyzed under a microscope, and the pathologist determines whether a carcinoid tumor is present. This provides a definite diagnosis of NET.