This article will help you read and understand your pathology report for adenocarcinoma of the stomach.
by Jason Wasserman, MD PhD FRCPC, updated December 23, 2020
The stomach is a hollow organ found near the middle of your abdomen. Food that you eat travels down your esophagus into the stomach. The stomach is responsible for breaking down and absorbing food so that it can be used by your body.
The stomach is made up of six layers of tissue:
Adenocarcinoma is a type of stomach cancer. It starts from the cells in the epithelium on the inside of the stomach. In many cases, adenocarcinoma starts from a pre-cancerous change called intestinal metaplasia. Intestinal metaplasia occurs when the epithelium normally found in the stomach becomes damaged and is replaced by the type of epithelium that is normally found in the small bowel.
The diagnosis of adenocarcinoma is usually made after a small sample of tissue is removed in a procedure called a biopsy. A test called immunohistochemistry may be performed to confirm the diagnosis. Your doctors will use the information found in your pathology report to plan treatment such as surgery, radiation, and chemotherapy.
After the tumour has been removed completely, it will be sent to a pathologist who will prepare another pathology report. This report will confirm or revise the original diagnosis and provide additional important information such tumour size, extension, and spread of tumour cells to lymph nodes. This information is used to determine the cancer stage and to decide if additional treatment is required.
Pathologists divide adenocarcinoma of the stomach into two different groups based on how the cells look when examined under the microscope. These groups are called histologic types and the two most common histologic types are intestinal-type and diffuse-type. Diffuse type is also called signet ring cell type.
The histologic type is important because the diffuse type has a higher chance of spreading to other parts of the body and is associated with worse prognosis.
There are other types of adenocarcinoma in the stomach but they are rare and will not be discussed in this article.
Grade is a word pathologists use to describe the difference between the tumour cells and normal, healthy tissue. Because most adenocarcinomas develop from from the pre-cancerous condition intestinal metaplasia (which looks like small bowel), the grade for adenocarcinoma of the stomach is actually is based on how different the cancer cells look compared to the cells in the small bowel.
The normal, healthy small bowel is made up of small round structures called glands. For this reason, adenocarcinoma is given a grade based on how much of the tumour is made up of glands:
Compared to well and moderately differentiated tumours, poorly differentiated tumours grow faster and are more likely to spread to other parts of the body.
HER2 is protein made by cells throughout the body. HER2 behaves like a switch that allows cells to grow and divide. Some cancer cells produce extra amounts of HER2 which allows them to grow and divide much faster than normal cells.
One out of every five tumours in the stomach produce extra HER2. For this reason, your pathologist will order a test to look for HER2 in the cancer cells.
If immunohistochemistry was performed on the tumour, your report will describe the results as:
Some treatments are only offered to patients with HER2 producing (positive) tumours. Talk to your doctor about the treatment options available for you.
This is the size of the tumour measured in centimetres. The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 4.0 cm by 2.0 cm by 1.5 cm, your report will describe the tumour as being 4.0 cm.
Tumour extension describes how far the cancer cells have spread from the epithelium into the layers of tissue below.
Your pathology report will describe the tumour extension as follows:
Tumour extension is important because it is used to determine the pathologic tumour stage (see Pathologic stage below). Cancer cells that have spread further into the stomach or surrounding organs are more likely to come back after treatment in the area of the original tumour or spread to another part of the body.
Nerves are like long wires made up of groups of cells called neurons. Nerves send information (such as temperature, pressure, and pain) between your brain and your body. Perineural invasion means that cancer cells were seen attached to a nerve.
Cancer cells that have attached to a nerve can use the nerve to travel into tissue outside of the tumour. This increases the risk that the tumour will come grow back in the same area of the body (recurrence) after treatment.
Blood moves around the body through long thin tubes called blood vessels. Another type of fluid called lymph which contains waste and immune cells moves around the body through lymphatic channels.
Cancer cells can use blood vessels and lymphatics to travel away from the tumour to other parts of the body. The movement of cancer cells from the tumour to another part of the body is called metastasis.
Before cancer cells can metastasize, they need to enter a blood vessel or lymphatic. This is called lymphovascular invasion.
Lymphovascular invasion increases the risk that cancer cells will be found in a lymph node or a distant part of the body such as the lungs. In particular, cancer cells seen inside a large vein outside of the tumour is associated with a high risk that the cancer cells will eventually be found in the lung or liver.
Lymph nodes are small immune organs located throughout the body. Cancer cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour (see Lymphovascular invasion above). The movement of cancer cells from the tumour to a lymph node is called a metastasis.
Your pathologist will carefully examine each lymph node for cancer cells. Lymph nodes that contain cancer cells are often called positive while those that do not contain any cancer cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain cancer cells.
Finding cancer cells in a lymph node is associated with an increased risk that the cancer cells will spread to other parts of the body. The number of lymph nodes with cancer cells is also used to determine the nodal stage (see Pathologic stage below).
A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. Whenever possible, surgeons will try to cut tissue outside of the tumour to reduce the risk that any cancer cells will be left behind after the tumour is removed.
The margins described in your report will depend on how much tissue was removed with the tumour. If the tumour was small and located in the middle of the stomach, all of the margins may be within the stomach. If the tumour was larger or located near the esophagus or small bowel, there may also be a margin in the esophagus or in an area of the small bowel called the duodenum.
Your pathologist will carefully examine all the margins in your tissue sample to see how close the cancer cells are to the edge of the cut tissue. Margins will only be described in your report after the entire tumour has been removed.
A margin is called positive when there are tumour cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will recur in the same site after treatment. A negative margin means that no tumour cells were seen at any of the cut edges of tissue.
If you received treatment (either chemotherapy or radiation therapy) for your cancer prior to the tumour being removed, your pathologist will examine all of the tissue submitted to see how much of the tumour is still alive (viable).
The treatment effect will be reported on a scale of 0 to 3 with 0 being no viable cancer cells (all the cancer cells are dead) and 3 being extensive residual cancer with no apparent regression of the tumour (all or most of the cancer cells are alive).
Lymph nodes with cancer cells will also be examined for treatment effect.
The pathologic stage for adenocarcinoma is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer.
This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M) to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means more advanced disease and worse prognosis.
Your pathologist will give a tumour stage from Tis to T4 based on how far the cancer cells have spread from the epithelium on the inner surface of the stomach into the tissue below.
Adenocarcinoma is given an nodal stage between N0 and N3 based on the number of lymph nodes with cancer cells.
Adenocarcinoma is given a metastatic stage between 0 and 1 based on the presence of cancer cells at a distant site in the body (for example the lungs). The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely present, the metastatic stage cannot be determined and is listed as MX.