Neuroendocrine Tumor of the Lung: Stages and Grades

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

ON THIS PAGE: You will learn about how doctors describe a tumor’s growth or spread. This is called the stage. In addition, you can read about how doctors compare cancer cells to healthy cells, called grading. Use the menu to see other pages.

Staging is a way of describing where the tumor is located, if or where it has spread, and whether it is affecting other parts of the body. Doctors use diagnostic tests to find out the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help inform a patient’s prognosis, which is the chance of recurrence or survival. There are different stage descriptions for different types of NETs.

The staging of a lung NET is the same as the staging of non-small cell lung cancer (NSCLC).

In general, a lower number stage is linked with a better outcome. However, no doctor can predict how long a patient will live with a lung NET based only on the stage of disease.

Cancer stage grouping

The stage of lung NET is based on a combination of several factors, including:

  • The size and location of the tumor

  • Whether it has spread to the lymph nodes and/or other parts of the body.

There are 5 stages for lung NETs: stage 0 (zero) and stages I through IV (1 through 4). One important treatment assessment is to find out whether the tumor can be completely removed by a surgeon. If it is possible, the surgeon must remove the tumor, along with the surrounding, healthy lung tissue. In general, the lymph nodes are also removed in a systematic fashion.

Stage 0

This is called in situ disease, meaning the tumor is “in place” and has not grown into nearby tissues and spread outside the lung. This tumor is not invasive.

Stage I

A stage I lung NET is a small tumor that has not spread to any lymph nodes. Stage I is divided into 2 substages based on the size of the tumor:

  • Stage IA tumors are 3 centimeters (cm) or less in size. Stage IA tumors may be further divided into IA1, IA2, or IA3, based on the size of the tumor.

  • Stage IB tumors are more than 3 cm but 4 cm or less in size.

Stage II

A stage II lung NET is divided into 2 substages:

  • Stage IIA describes a tumor larger than 4 cm but 5 cm or less in size that has not spread to the nearby lymph nodes.

  • Stage IIB describes a tumor that is 5 cm or less in size that has spread to the lymph nodes. Or, stage IIB can describe be a tumor more than 5 cm wide that has not spread to the lymph nodes.

Stage III

Stage III lung NETs are classified as either stage IIIA, IIIB, or IIIC. The stage is based on the size of the tumor and which lymph nodes the cancer has spread to. Stage III cancers have not spread to other distant parts of the body.

For many stage III cancers, the tumor is difficult, and sometimes impossible, to remove with surgery. For example, the lung NET may have spread to the lymph nodes located in the center of the chest, which is outside the lung. Or, the tumor may have grown into nearby structures in the lung. In either situation, it is less likely that the surgeon can completely remove the cancer. Sometimes it is not possible to remove lung NETs if they have spread to the lymph nodes above the collarbone or if they have grown into vital structures within the chest. These vital structures include the heart, large blood vessels, or the main breathing tubes leading to the lungs.

Stage IV

Stage IV means the lung NET has spread to more than 1 area in the opposite lung, the fluid surrounding the lung or the heart, or distant parts of the body through the bloodstream. Once cancer cells get into the blood, the cancer can spread anywhere in the body. A lung NET is more likely to spread to the brain, bones, liver, and adrenal glands. Stage IV is divided into 2 substages:

  • Stage IVA cancer has spread within the chest, such as the opposite lung or the lining of the heart or lung, and/or has spread to only 1 area outside of the chest.

  • Stage IVB has spread outside of the chest, with more than 1 metastases outside the lung, in 1 or more organs.

In general, surgery is not successful for most stage IV lung NETs. In these situations, the doctor will recommend other treatment options.

Grade (G)

Doctors also describe a lung NET by its grade (G). The grade describes how much tumor cells look like healthy cells when viewed under a microscope. The doctor compares the cancerous tissue with healthy tissue. Healthy tissue usually contains many different types of cells grouped together. If the cancer looks similar to healthy tissue, it is called “differentiated” or a “low-grade tumor.” If the cancerous tissue looks very different from healthy tissue, it is called “poorly differentiated” or a “high-grade tumor.”

For NETs, the grade describes how fast the tumor cells are growing and dividing, a process called mitosis, as well as whether there are dead cells in the tumor, which is called necrosis.

The tumor’s grade may help the doctor predict how quickly the cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.

GX: The tumor grade cannot be identified.

G1: The cells are more like healthy cells (called well differentiated), also called “typical carcinoid.” A limited number of cells are dividing, when measured by a tool called the mitotic index. The mitotic index is less than 2, and there is no necrosis.

G2: The cells are somewhat like healthy cells (called moderately differentiated), also called “atypical carcinoid.” The mitotic index is 2 to 10, meaning an intermediate number of cells is dividing. The tumor may outgrow its blood supply in the area, which will lead to necrosis.

G3: The cells look less like healthy cells (called poorly differentiated). The mitotic index is more than 10, meaning that a large number of cells are dividing, or the tumor has outgrown its blood supply in many areas, which will lead to cell death (necrosis).

Recurrent NETs

Recurrent cancer is cancer that has come back after treatment. If the NET does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.

Used with permission of the American College of Surgeons, Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017), published by Springer International Publishing.

Information about the tumor’s stage and grade will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.