Staging is the process of finding out how far a cancer has spread. The extent of spread of stomach cancer is an important factor in choosing treatment options and predicting a patient's outlook (prognosis). The tests described in the section "How is stomach cancer diagnosed?" are the ones used to determine the stage of the cancer.
The stage of a cancer does not change over time, even if the cancer progresses. A cancer that comes back or spreads is still referred to by the stage it was given when it was first found and diagnosed, only information about the current extent of the cancer is added. A person keeps the same diagnosis stage, but more information is added to explain the current disease status
The stage of a stomach cancer can be based either on the results of physical exams, biopsies, and imaging tests (called the clinical stage), or on the results of these tests plus the results of surgery (called the pathologic stage). The staging described here is the pathologic stage, which includes the findings from the tissues removed during surgery. Pathologic staging is likely to be more accurate than clinical staging, as it allows the doctor to get a firsthand impression of the extent of the cancer.
A staging system is a way for members of the cancer care team to describe the extent of a cancer's spread. The system most often used to stage stomach cancer in the United States is the American Joint Commission on Cancer (AJCC) TNM system. The TNM system for staging contains 3 key pieces of information:
- T describes the extent of the primary tumor (how far it has grown into the wall of the stomach and into nearby organs).
- N describes the spread to nearby (regional) lymph nodes.
- M indicates whether the cancer has metastasized (spread) to other organs of the body. (The most common sites of distant spread of stomach cancer are the liver, the peritoneum (the lining of the space around the digestive organs), and distant lymph nodes. Less common sites of spread include the lungs and brain.)
Numbers or letters appear after T, N, and M to provide more details about each of these factors:
- The numbers 0 through 4 indicate increasing severity.
- The letter X means "cannot be assessed" because the information is not available.
- The letters "is" mean "carcinoma in situ," which means the tumor is contained within the top layer of mucosa cells and has not yet invaded deeper layers of tissue.
This system is for staging all stomach cancers except those either starting in the gastroesophageal junction (where the stomach and the esophagus meet) or starting in the cardia (the first part of the stomach) and growing into the gastroesophageal junction. Those cancers are staged (and often treated) like cancers of the esophagus.
T categories of stomach cancer
The T category describes how far down through the stomach's 5 layers the cancer has invaded. The innermost layer is the mucosa. This is where stomach acid and digestive enzymes are made. The mucosa has 3 parts: epithelial cells, which lie on top of a layer of connective tissue (the lamina propria), which is on top of a thin layer of muscle (the muscularis mucosa). Under the mucosa is a supporting layer called the submucosa. This is surrounded by the muscularis, a layer of muscle that moves and mixes the stomach contents. The next 2 layers, the subserosa and the outermost serosa, act as wrapping layers for the stomach.
TX: The main tumor cannot be assessed.
T0: No signs of a main tumor can be found.
Tis: Cancer cells are only in the top layer of cells of the mucosa (innermost layer of the stomach) and have not grown into deeper layers of tissue such as the lamina propria or muscularis mucosa. This stage is also known as carcinoma in situ.
T1: The tumor has grown from the top layer of cells of the mucosa into the next layers below such as the connective tissue (lamina propria), the muscularis mucosa, or submucosa.
- T1a: The tumor is growing into the lamina propria or muscularis mucosa.
- T1b: The tumor has grown through the lamina propria and muscularis mucosa and into the submucosa.
T2: The tumor is growing into the muscularis propria layer.
T3: The tumor is growing into the subserosa layer.
T4: The tumor has grown through the stomach wall and into the serosa and may be growing into a nearby organ (spleen, intestines, pancreas, kidney, etc.) or other structures such as major blood vessels.
- T4a: The tumor has grown through the stomach wall into the serosa (the outer covering of the stomach), but the cancer hasn't grown into any of the nearby organs or structures.
- T4b: The tumor has grown through the stomach wall and into nearby organs or structures.
N categories of stomach cancer
NX: Regional lymph nodes cannot be assessed.
N0: No spread to nearby (regional) lymph nodes.
N1: The cancer has spread to a few (1 to 2) nearby lymph nodes.
N2: The cancer has spread to some (3 to 6) nearby lymph nodes.
N3: The cancer has spread to many (more than 7) nearby lymph nodes.
- N3a: The cancer has spread to 7 to 15 nearby lymph nodes.
- N3b: The cancer has spread to 16 or more nearby lymph nodes.
M categories of stomach cancer
M0: No distant metastasis (the cancer has not spread to distant organs or sites, such as the lungs or brain).
M1: Distant metastasis (spread of the cancer to organs or lymph nodes far away from the stomach).
TNM Stage Grouping
The T, N, and M categories are combined and expressed as a stage, using the number 0 (zero) and the Roman numerals I through IV. This is known as stage grouping. Some stages are split into substages, indicated by letters.
Stage 0: Tis, N0, M0
This is cancer in its earliest stage. It has not grown beyond the inner layer of cells that line the stomach. The cancer has not spread to any lymph nodes (N0) or anywhere else (M0). This stage is also known as carcinoma in situ.
Stage IA: T1, N0, M0
The cancer has grown beneath the top layer of cells in the mucosa into tissue below, such as the connective tissue (lamina propria), the thin muscle layer (muscularis mucosa), or the submucosa (T1). But it has not grown into the main muscle layer of the stomach, called the muscularis propria. The cancer has not spread to any lymph nodes (N0) or anywhere else (M0).
Stage IB: Any of the following:
T1, N1, M0: Just as in stage IA, the cancer has grown into the layer of connective tissue (lamina propria), and may have grown into the thin layer of muscle beneath it (muscularis mucosa) or deeper into the submucosa (T1). It has not grown into the muscularis propria, the main muscle layer of the stomach. Cancer has also spread to 1 or 2 lymph nodes near the stomach (N1), but not to any other tissues or organs (M0).
OR
T2, N0, M0: The cancer has grown into the main muscle layer of the stomach wall, called the muscularis propria (T2). It has not spread to nearby lymph nodes (N0) or to any other tissues or organs (M0).
Stage IIA: Any of the following:
T1, N2, M0: The cancer has grown beneath the top layer of cells of the mucosa into the layer of connective tissue (lamina propria), thin muscle layer (muscularis mucosa), or the submucosa (T1). It has not grown into the main muscle layer, but it has spread to between 3 and 6 lymph nodes near the stomach (N2). It has not spread to distant sites (M0).
OR
T2, N1, M0: The cancer has grown into the main muscle layer of the stomach called the muscularis propria (T2). It has spread to 1 or 2 nearby lymph nodes (N1), but has not spread to distant sites (M0).
OR
T3, N0, M0: The cancer has grown through the main muscle layer into the subserosa, but has not grown through all the layers to the outside the stomach (T3). It has not spread to any nearby lymph nodes (N0) or to tissues or organs outside of the stomach (M0).
Stage IIB: Any of the following:
T1, N3, M0: The cancer has grown beneath the top layer of cells of the mucosa into the layer of connective tissue (lamina propria), the thin muscle layer, or the submucosa (T1). It has not grown into the main muscle layer, but it has spread to 7 or more lymph nodes near the stomach (N3). It has not spread to tissues or organs outside the stomach (M0).
OR
T2, N2, M0: The cancer has grown into the main muscle layer (T2). It has spread to between 3 and 6 lymph nodes near the stomach (N2), but it has not spread to any tissues or organs outside the stomach (M0).
OR
T3, N1, M0: The cancer has grown into the subserosa layer, but not completely through all the layers to the outside of the stomach (T3). It has spread to 1 or 2 nearby lymph nodes (N1), but has not spread to tissues or organs outside the stomach (M0).
OR
T4a, N0, M0: The cancer has grown completely through all the layers of stomach wall into the outer covering of the stomach (the serosa), but has not started growing into other nearby organs or tissues, such as the spleen, intestines, kidneys, or pancreas (T4a). It has not spread to any nearby lymph nodes (N0) or distant sites (M0).
Stage IIIA: Any of the following:
T2, N3, M0: The cancer has grown into the main muscle layer (T2). It has spread to 7 or more lymph nodes near the stomach (N3), but has not spread to tissues or organs outside the stomach (M0).
OR
T3, N2, M0: The cancer has grown into the subserosa layer, but not completely through all the layers to the outside of the stomach (T3). It has spread to between 3 and 6 nearby lymph nodes (N2), but has not spread to tissues or organs outside the stomach (M0).
OR
T4a, N1, M0: The cancer has grown completely through all the layers of the stomach wall into the outer covering of the stomach (the serosa), but has not started growing into nearby organs or tissues (T4a). It has spread to 1 or 2 nearby lymph nodes (N1), but has not spread to distant sites (M0).
Stage IIIB: Any of the following:
T3, N3, M0: The cancer has grown into the subserosa layer, but not completely through all the layers to the outside of the stomach (T3). It has spread to 7 or more nearby lymph nodes (N2), but has not spread to distant sites (M0).
OR
T4a, N2, M0: The cancer has grown completely through all the layers of the stomach wall into the serosa (the outer covering of the stomach), but has not started growing into nearby organs or tissues (T4a). It has spread to 3 to 6 nearby lymph nodes (N2), but has not spread to distant sites (M0).
OR
T4b, N0 or N1, M0: The cancer has grown through the stomach wall and into nearby organs or structures (such as the spleen, intestines, liver, pancreas, or major blood vessels) (T4b). It may also have spread to up to 2 nearby lymph nodes (N0 or N1). It has not spread to distant sites (M0).
Stage IIIC: Any of the following:
T4a, N3, M0: The cancer has grown completely through all the layers of the stomach wall into the serosa, but has not started growing into nearby organs or tissues (T4a). It has spread to 7 or more nearby lymph nodes (N3), but has not spread to distant sites (M0).
OR
T4b, N2 or N3, M0: The cancer has grown through the stomach wall and into nearby organs or structures (such as the spleen, intestines, liver, pancreas, or major blood vessels) (T4b). It has spread to 3 or more nearby lymph nodes (N2 or N3). It has not spread to distant sites (M0).
Stage IV: Any T, any N, M1:
The cancer has spread to distant organs such as the liver, lungs, brain, or bones (M1).
If you have any questions about the stage of your disease, ask your doctor to explain this to you. The stage of a stomach cancer is an important factor, but it is not the only factor in considering treatment options and in predicting outlook for survival.
Resectable vs. unresectable cancer
Resectable cancers are those the doctor believes can be completely removed during surgery. Unresectable cancers can't be removed completely. This might be because the tumor has grown too far into nearby organs or lymph nodes, it has grown too close to major blood vessels, or it has spread to distant parts of the body. There is no distinct dividing line between resectable and unresectable in terms of the TNM stage of the cancer, but earlier stage cancers are more likely to be resectable.
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