The American Joint Committee on Cancer (AJCC) TNM system divides stomach cancer into stages 0–4. The higher the stage, the more difficult it is to treat and to survive.

The most commonly used system for staging stomach cancer is the AJCC’s TNM system. This system classifies cancer from stage 0 to 4 based on three features:

  • T: tumor size
  • N: number of nearby lymph nodes affected
  • M: metastasis, whether cancer has spread to distant areas

In this article, we look at how doctors determine which stage your cancer is in.

Types of stomach cancer

About 90–95% of stomach cancers develop in glandular tissue and are classified as adenocarcinoma. Less common types include:

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The AJCC’s staging system is used for all stomach cancers except for cancers that start:

  • where your stomach and esophagus meet
  • in your upper stomach and spread to your esophagus

In these cases, cancer is usually staged as esophageal cancer.

Stomach wall layers

Your stomach wall is made up of five layers. From the innermost to the outermost layer, they’re the:

  • mucosa
  • submucosa
  • muscularis
  • subserosa
  • serosa
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AJCC staging system

Here’s a look at the AJCC system.

AJCC stageTNM groupingDescription
Stage 0 (precancer or carcinoma in situ)• Tis
• N0
• M0		You have abnormal-looking cells in your stomach lining or cancer cells on the top layer of your mucosa.
Stage 1A• T1
• N0
• M0		Your tumor has grown into your mucosa or submucosa.
Stage 1B•T1
•N1
•M0

OR

• T2
• N0
• M0		Your tumor has grown into your mucosa or submucosa. It has spread to 1–2 nearby lymph nodes.

OR

Your tumor has spread into the muscularis layer but not into lymph nodes.

Stage 2A• T1
• N2
• M0

OR

• T2
• N1
• M0

OR

• T3
• N0
• M0		Your tumor has grown into your mucosa or submucosa. It has spread to 3–6 nearby lymph nodes.

OR

The cancer has grown into the muscularis layer and spread to 1–2 nearby lymph nodes.

OR

The cancer has grown into the subserosa layer but not lymph nodes.
Stage 2B• T1
• N3a
• M0

OR

• T2
• N2
• M0

OR

• T3
• N1
• M0

OR

• T4a
• N0
• M0		Your tumor has grown into your mucosa or submucosa. It has also spread to 7–15 nearby lymph nodes.

OR

The cancer has grown into the muscularis layer and spread to 3–6 lymph nodes.

OR

The tumor has grown into the subserosa layer and spread to 1–2 nearby lymph nodes.

OR

The tumor has grown through your stomach wall to the serosa but hasn’t spread to other structures or lymph nodes.
Stage 3A• T2
• N3a
• M0

OR

• T3
• N2
• M0

OR

• T4a
• N1 or N2
• M0

OR

• T4b
• N0
• M0 		The tumor has grown into the muscularis layer and to 7–15 nearby lymph nodes.

OR

The tumor has grown into the subserosa and to 3–6 nearby lymph nodes.

OR

The tumor has grown through the stomach wall to the serosa but not to other structures. It has spread to 1–6 nearby lymph nodes.

OR

The cancer has grown through the stomach wall and into nearby organs or structures but not lymph nodes or distant locations.
Stage 3B• T1
• N3b
• M0

OR

• T2
• N3b
• M0

OR

• T3
• N3a
• M0

OR

• T4a
• N3a
• M0

OR

• T4b
• N1 or 2
• M0		The cancer has grown into your mucosa or submucosa. It has also spread to 16 or more nearby lymph nodes.

OR

The tumor has grown into the muscularis layer and 16 or more nearby lymph nodes.

OR

The tumor has grown into the subserosa layer and 7–15 lymph nodes.

OR

The tumor has grown through the stomach wall but not into nearby organs or structures. It has spread to 7–15 nearby lymph nodes.

OR

The main tumor has grown into the stomach wall and into nearby structures. It’s also spread to 1–6 nearby lymph nodes.
Stage 3C• T3
• N3b
• M0

OR

• T4a
• N3b
• M0

OR

• T4b
• N3 or N3b
• M0		The tumor has grown into the subserosa and has spread to 16 or more lymph nodes.

OR

The tumor has grown through the stomach wall into the serosa but not into nearby organs or structures. It has spread to 16 or more lymph nodes.

OR

The tumor has grown through the stomach wall and into nearby structures. It has spread to at least 7 nearby lymph nodes.
Stage 4• Any T
• Any N
• M1		The cancer has spread to distant locations. The primary tumor can be any size and can have spread to any number of lymph nodes.

Stomach cancer usually grows for many years before it becomes large enough to cause symptoms. A lack of early symptoms makes it hard to catch while it’s still contained in your stomach.

Almost all stomach cancers are adenocarcinoma, which can be subdivided into intestinal gastric adenocarcinoma and diffuse gastric adenocarcinoma.

Most adenocarcinomas are the intestinal subtype. About 30% of adenocarcinomas are the diffuse subtype, and another 15–20% have mixed features of both types. Diffuse gastric carcinoma tends spreads quicker, and people with this cancer tend to have a poorer outlook.

The most common distant location stomach cancers spread to include your liver, lung, and bone.

The American Cancer Society and National Cancer Institute report survival statistics using a simpler staging system. Here’s a look at the 5-year relative survival rates from 2012 to 2018 in the United States:

StageAJCC equivalent5-year survival rate
LocalizedStage 1 or 272%
RegionalStage 2 or 333%
DistantStage 46%
All stages–33%

Some factors linked to better survival include:

  • not having HER2-positive cancer
  • cancer in the lower stomach
  • having the subtype intestinal adenocarcinoma
  • younger age and better overall health

The most common staging system for stomach cancer is the AJCC’s TNM system. This staging system divides cancer into stages 0–4.

Higher stages of stomach cancer are more difficult to treat. Stage 4 stomach cancer usually isn’t considered curable.