Small Bowel Cancer: Stages and Grades

Approved by the Cancer.Net Editorial Board, 04/2022

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

What is cancer staging?

Staging is a way of describing where the cancer 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 the tests are finished. Knowing the stage helps the doctor recommend the best kind of treatment, and it can help predict a patient's prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancers.

This page provides detailed information about the system used to find the stage of small bowel adenocarcinoma and the stage groups for small bowel adenocarcinoma, such as stage II or stage IV. Other types of small bowel cancer are staged differently (see the Introduction for more information).

TNM staging system for small bowel adenocarcinoma

One tool that doctors use to describe the stage is the TNM system. Doctors use the results from diagnostic tests and scans to answer these questions:

  • Tumor (T): How large is the primary tumor? Where is it located?

  • Node (N): Has the tumor spread to the lymph nodes? If so, where and how many?

  • Metastasis (M): Has the cancer spread to other parts of the body? If so, where and how much?

The results are combined to determine the stage of cancer for each person.

There are 5 stages: stage 0 (zero) and stages I through IV (1 through 4). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

Tumor (T)

Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe the location of the small bowel tumor. Tumor size is measured in centimeters (cm). A centimeter is roughly equal to the width of a standard pen or pencil.

Stage may also be divided into smaller groups that help describe the tumor even in more detail. This helps the doctor develop the best treatment plan for each patient. Specific tumor stage information is listed below.

The primary tumor cannot be evaluated.

T0 (T zero): There is no evidence of a primary tumor.

Tis: This refers to carcinoma (cancer) in situ. Cancer in situ is very early cancer in which cancer cells are found only in 1 small area and have not spread.

T1a: There is a tumor in the lamina propria, the innermost layer of the small bowel.

T1b: There is a tumor in the submucosa, the next deepest layer of the small bowel.

T2: The tumor is in the muscularis propria, the third layer of the small bowel.

The tumor has grown through the muscularis propria and into the subserosa, a thin layer of connective tissue beneath the outer layer of some parts of the large intestine, or into certain tissues surrounding the small bowel.

The tumor has invaded other organs or has grown through the lining of the abdominal cavity, the space between the abdomen and the spine that holds several organs, called the visceral peritoneum.

Node (N)

The “N” in the TNM staging system stands for lymph nodes. These small, bean-shaped organs help fight infection. Lymph nodes near the small bowel are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.

NX: The regional lymph nodes cannot be evaluated.

N0 (N zero):
There is no cancer in the regional lymph nodes.

Cancer has spread to 1 to 2 regional lymph nodes.

N2: Cancer has spread to 3 or more regional lymph nodes.

Metastasis (M)

The “M” in the TNM system describes whether the cancer has spread to other parts of the body, called metastasis.

MX: Distant metastasis cannot be evaluated.

M0 (M zero):
There is no metastasis.

There is distant metastasis, meaning the cancer has spread to other parts of the body beyond the small bowel.

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Stage groups for small bowel adenocarcinoma

Doctors combine the T, N, and M information (see above) to say what stage the cancer is.

Stage 0: This refers to cancer in situ. The cancer is found in only 1 place and has not spread (Tis, N0, M0).

Stage I:
The cancer has grown through the inner layers of the small bowel. It has not spread into nearby tissue or lymph nodes (T1 or T2, N0, M0).

Stage IIA:
The cancer has spread through the wall of the small bowel, and it may have spread to nearby tissue. It has not spread to the nearby lymph nodes (T3, N0, M0).

Stage IIB:
The cancer has invaded nearby structures outside of the small bowel, but it has not spread to the nearby lymph nodes (T4, N0, M0).

Stage IIIA: The cancer has spread to 1 to 3 regional lymph nodes. It may or may not have grown through the inner lining or into the muscle layers of the small bowel, but it has not spread to other parts of the body (any T, N1, M0).

Stage IIIB: The cancer has spread to 4 or more regional lymph nodes. It may or may not have grown through the inner lining or into the muscle layers of the small bowel, but it has not spread to other parts of the body (any T, N2, M0).

Stage IV: The cancer has spread to other parts of the body, such as the liver or lungs (any T, any N, M1).

Recurrent cancer is cancer that has come back after treatment. The disease may return in the colon, rectum, or another part of the body. If the cancer 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.

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Grade (G)

Doctors also describe small bowel cancer by its grade (G). The grade describes how much cancer 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 and has different cell groupings, 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.” The cancer’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 look more like normal tissue cells (well differentiated).

G2: The cells are somewhat different (moderately differentiated).

G3: The cells look very unlike normal cells (poorly differentiated).

G4: The cells barely resemble normal cells (undifferentiated).

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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 cancer’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.