Neuroendocrine Tumor of the Lung: Introduction

Approved by the Cancer.Net Editorial Board, 12/2019

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Neuroendocrine Tumor of the Lung. Use the menu to see other pages. Think of that menu as a roadmap for this complete guide.

About neuroendocrine tumors

A tumor begins when the DNA of healthy cells is damaged, causing the cells to grow out of control, forming a mass. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body if it is not found early and treated.

A neuroendocrine tumor (NET) begins in the specialized cells of the body’s neuroendocrine system. These cells have traits of both hormone-producing endocrine cells and nerve cells. They are found throughout the body’s organs and help control many of the body’s functions. Hormones are chemical substances that are carried through the bloodstream to have a specific effect on the activity of other organs or cells in the body. All NETs are considered malignant tumors. Most NETs take years to develop and grow slowly. However, some NETs can be fast-growing. See the Stages and Grades section to learn more.

NETs develop most commonly in the lung or the gastrointestinal (GI) tract (learn more about GI tract NETs). Lung NETs are also called carcinoid tumors or carcinoids. NETs can also develop in the pancreas (learn more about NETs of the pancreas) and other locations throughout the body. Rare types of NET that develop in or on the adrenal glands are called pheochromocytoma or paraganglioma. Learn more about NETs that develop in other parts of the body.

The rest of this guide is about lung NETs.

About lung NETs

While most NETs begin in the GI tract, about 30% occur in the bronchial system, or airways, of the lungs. When a person inhales, the bronchial system carries air to the lungs. The lungs absorb oxygen from the air and bring the oxygen into the bloodstream so it can be delivered to the rest of the body. As the body’s cells use oxygen, they release carbon dioxide. The bloodstream carries carbon dioxide back to the lungs, and the carbon dioxide leaves the body when a person exhales.

A small number of lung NETs can make high levels of hormone-like substances called neuropeptides and amines. If these substances are released in high amounts, they may lead to a group of symptoms called carcinoid syndrome (see Symptoms and Signs). However, if these substances are released in smaller amounts, then there may be no symptoms of the developing NET.

Types of lung NETs

There are 2 types of lung NETs: typical carcinoids and atypical carcinoids. There are other types of NETs that develop in the lung, called small cell neuroendocrine carcinoma (or small cell lung cancer) and large cell neuroendocrine carcinoma (a type of non-small cell lung cancer). The type of lung NET is defined by the pathologist and based on how much cancer cells look like healthy cells when viewed under a microscope. In addition, the categories are based on the number of dividing cells, called the mitotic index, and whether there are dead cells in the tumor, which is called necrosis. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

Typical and atypical carcinoids can grow slowly for years without being found. Although these types of lung NETs are cancerous, they are often described as "cancer in slow motion."

NETs are also described as “functional” or “non-functional.” Functional NETs release enough neuropeptides and amines to cause symptoms. Non-functional NETs do not release enough substances to cause symptoms.

The next section in this guide is Statistics. It helps explain the number of people who are diagnosed with a lung NET and general survival rates. Use the menu to choose a different section to read in this guide.