Pulmonary neuroendocrine tumors are often found during imaging studies that are performed to diagnose other types of lung conditions or for other health issues.
If a carcinoid tumor is suspected, blood and urine tests may be performed to look for abnormal amounts of hormones and other substances (peptides) produced by the tumor, including chromagranin A (a protein commonly found in many carcinoid tumors), serotonin, and 5HIAA (a byproduct of serotonin).
Imaging tests also may be performed to determine the exact location and size of the tumor, whether or not it has spread to other organs, and if it can be removed with surgery.
This type of imaging test provides a three-dimensional picture of the inside of the body and may be used to determine whether a pulmonary neuroendocrine tumor has spread to the liver or nearby lymph nodes. Sometimes a dye is given intravenously to help provide better detail.
OctreoScan (Somatostatin Receptor Scintigraphy) Imaging
The surface of most carcinoid tumors contains several receptors for somatostatin — a substance that suppresses the production of hormones involved in growth, metabolism, and digestion. Patients suspected of having a carcinoid tumor receive an injection of octreotide, a synthetic form of somatostatin, and a small amount of a radioactive substance (radionuclide). The radioactive octreotide binds to somatostatin receptors, which appear as bright spots on imaging tests, indicating the presence of a tumor. Carcinoid tumors may be treated with octreotide therapy (described in the Treatment section).
A small amount of radionuclide is given intravenously, where it is absorbed by the organs to be studied. The radionuclide produces energy that is detected by a scanner. This type of imaging test is helpful in diagnosing more aggressive types of carcinoid tumors, such as atypical carcinoid tumors.
The doctor may insert a thin, flexible tube attached to a small camera through the mouth into the windpipe to identify the location of the tumor and determine whether it can be surgically removed.
In addition, a biopsy (tissue sample) of the tumor may be required to make a definitive diagnosis of the tumor and its characteristics. Our pathologists are specially trained to identify subtle clues that indicate whether a tumor is low grade, such as carcinoid tumors that often grow slowly over time, or high grade, such as large cell or small cell lung tumors that contain rapidly dividing cells. Understanding these differences can have an important influence on the type of treatment selected for each patient.