Small Intestine Cancer (Adenocarcinoma) Stages

After someone is diagnosed with small intestine cancer, doctors will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes the extent of the cancer in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

The earliest stage small intestine cancers are called stage 0 (carcinoma in situ), and then range from stages I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

Small intestine cancers are typically given a clinical stage based on the results of any exams, biopsies, and imaging tests that might have been done. If surgery has been done, the pathologic stage (also called the surgical stage) can also be determined.

Small intestine cancers typically start in the inner lining of the intestine. As they grow, they can spread into deeper layers. These layers include:

• Mucosa: This is the innermost layer. It has 3 parts: the top layer of cells (called the epithelium), a thin layer of connective tissue (called the lamina propria), and a thin layer of muscle (called the muscularis mucosa).
• Submucosa: This is the fibrous tissue that lies beneath the mucosa.
• Thick muscle layers (muscularis propria): This layer of muscle contracts to force the food along the GI tract.
• Subserosa and serosa: These are the thin outermost layers of connective tissue that cover the GI tract. The serosa is also known as the visceral peritoneum.

The AJCC TNM staging system

The staging system most often used for small intestine cancer is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

• The extent (size) of the main tumor (T): How far has the cancer grown into the layers of the wall of the small intestine? Has the cancer reached nearby structures or organs?
• The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
• The spread (metastasis) to distant sites (M): Has the cancer spread to distant parts of the body? The most common sites of spread are the liver and the inner lining of the abdomen (peritoneal cavity).

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

Once the T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more information see Cancer Staging.

The system described below is the most recent AJCC system, effective January 2018. It is only used for staging adenocarcinoma of the small intestine.

Small intestine cancer staging can be complex. If you have any questions about the stage of your cancer or what it means, ask your doctor to explain it to you in a way you understand.  

Stages of small intestine adenocarcinoma

AJCC Stage	Stage grouping	Stage description*
0	Tis N0 M0	The cancer is only in the epithelium (the top layer of cells of the mucosa). It has not grown into the deeper tissue layers (Tis).  It has not spread to nearby lymph nodes (N0) or distant parts of the body (M0).
I	T1 or T2 N0 M0	The cancer has grown into deeper layers (the lamina propria or the submucosa) (T1) OR it has grown through the submucosa into the muscularis propria (T2). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIA	T3 N0 M0	The cancer has grown through the muscularis propria and into the subserosa. It has not started to grow into any nearby organs or structures (T3). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIB	T4 N0 M0	The cancer has grown through the outer layer of tissue covering the intestine (the serosa or visceral peritoneum) or into nearby organs or structures (T4). The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IIIA	Any T N1 M0	The cancer might have grown into any layers of the wall of the small intestine (Any T). It has spread to 1 or 2 nearby lymph nodes (N1) but not to distant parts of the body (M0).
IIIB	Any T N2 M0	The cancer might have grown into any layers of the wall of the small intestine (Any T). It has spread to 3 or more nearby lymph nodes (N2) but not to distant parts of the body (M0).
IV	Any T Any N M1	The cancer might have grown into any layers of the wall of the small intestine (Any T). It might or might not have spread to nearby lymph nodes (Any N). It has spread to distant lymph nodes or organs such as the liver or the peritoneum (the inner lining of the abdomen) (M1).

* The following additional categories are not listed on the table above: 

• TX: Main tumor cannot be assessed due to lack of information.
• T0: No evidence of a main tumor.
• NX: Nearby lymph nodes cannot be assessed due to lack of information.