Understanding Your Pathology Report: An Overview

Like many cancers, colorectal cancer can be detected through various screening methods and tests, and their severity can sometimes also be estimated just by looking. However, a biopsy is usually required in order to fully ascertain if cancer is present and also determine how extensive it is.

A biopsy is a procedure to remove or extract a sample of cells or tissue and test the sample in a laboratory. In the context of cancer, a biopsy can retrieve tissue samples from growths that are suspected to be cancerous. Thanks to recent advancements, a blood sample may also be tested for signs of cancer, in a procedure known as liquid biopsy.

There are many ways to conduct a biopsy, and it usually depends on the location of the cancer. Some of the more common types of biopsy include needle biopsy (sometimes called fine needle aspiration biopsy), image-guided biopsy, shave or punch biopsy and laparoscopic biopsy.

For colorectal cancer though, biopsies are usually conducted during a colonoscopy by inserting the necessary tools through the colonoscope to remove the tissue. If you have been scheduled for surgery to remove polyps or other growths, the tissue sample is collected during the surgery.

The tissue samples can be collected from either tumors or polyps or other sections of the colon that your doctor suspects to be affected by cancer. This tissue sample is sent to a laboratory where a specialist known as a pathologist will examine the tissue under a microscope for cancer cells. The findings are consolidated in a biopsy or pathology report, which can take a few days to a couple of weeks depending on whether the initial findings require further testing and investigation.

Although a pathology report gives you a comprehensive summary of your condition, it can be a daunting task filtering through the medical jargon and understanding the key takeaways.

Aside from your personal details, the pathology report also includes basic information such as your initial diagnosis, attending physician, as well as the procedure you’ve undergone and where the tissue sample in question was removed from. These details can be found in a summary at the top of the report. The summary may also include confirmation of any cancer and the stage it is at.

Depending on whether you’ve begun to receive treatment such as chemotherapy or radiation therapy to reduce the size of the tumor, or if you’ve had other bowel conditions, these will also be indicated under clinical information.

Thereafter, the pathology report begins to cover the findings of your tissue sample, starting with a gross or macroscopic description of how it appears to the naked eye. The details such as the weight and size of the sample, its color and shape are documented as reference. Similar to a colonoscopy report, any polyps found are also described and recorded. These details alone, however, are not crucial in understanding your diagnosis.

What is pertinent, however, is the microscopic description, which explains the findings from observing the tissue sample under a microscope. It first indicates where the tumor is located in the colon, and so some preliminary knowledge of the colon’s anatomy would be useful.

Tumor cell and polyp types

The report also provides information on the cells found in the tissue sample and if these are cancerous. For cancer cells, the report identifies the tumor cell type, that is, the sort of cell the tumor arises from. For colorectal cancer, adenocarcinoma is the leading cause, where the tumor first develops from cells in the intestinal lining that make up the mucosa. Other types of colorectal cancer tumors include:

• Carcinoid tumors, also called neuroendocrine tumors (hormone producing cells)
• Gastrointestinal stromal tumor (intestinal muscle tissue)
• Sarcoma (muscle layers, connective tissue and blood vessels)
• Lymphoma (lymph nodes)

Polyp tissue would also be described in this section. While polyps are benign growths, the cells found in the polyp can serve as good indicators of the likelihood of developing into cancerous tumors. Adenomatous polyp tissue with tubular or villous growth patterns have a high chance of becoming cancerous, with villous tissue indicating more aggressive and rapid spread. Hyperplastic polyps are unlikely to develop into cancer.

Histological grade

The histological grade of a cell, as defined by the National Cancer Institute, refers to “how abnormal the cancer cells and tissue look under a microscope and how quickly the cancer cells are likely to grow and spread”. What does it mean for cancer cells to be “abnormal”?

In normal cell division, newly formed cells become specialized in a process known as differentiation, which leads to the cells having different functions and sometimes different appearances as they mature. Aggressive cancer cells are known to be poorly differentiated and bear little resemblance to the normal cells they are found with, while those that are better differentiated are considered low-grade and less aggressive. The histological grade thus determines how closely a cancer resembles a normal cell.

The histological tumor grades (G) can be described as follows:

It is important to note that histological tumor grading is not the same as cancer staging, which, based on the American Joint Committee on Cancer (AJCC) TNM system, is concerned with the size and extent of the tumor (T) and how many layers of the large intestine it has spread to, if it has spread to the lymph nodes (N) and if it has metastasized (M) to other distant organs of the body.

Depth of invasion

The crux of your pathology report are the sections that are crucial in determining your cancer stage.

The depth of invasion is concerned with how many layers of your colon wall the cancer cells have spread to and if it has completely penetrated through the layers. Cancer with low T stage have tumors that have not grown beyond the submucosa (the inner layers of the colon) and muscularis propria (outer muscle layer of the colon), corresponding with stages T1 and T2, while involvement of the tissue around the colonic wall (subserosa and serosa layers) are considered higher stage (stages T3 and T4). The deeper the tumor invades into the wall, the higher the risk of metastasis becomes.

Lymphovascular invasion

When examining the surrounding tissue, the pathologist will also check the blood vessels and lymphatic vessels for any cancer cells, as this is how cancer begins to spread to other parts of the body from the primary tumor. The presence of tumor in lymphatic vessels is a risk for lymph node metastasis, however it is possible to see tumors in lymphatic spaces but not identify any tumor within the lymph nodes themselves. Tumor present within veins is a risk factor for metastases to the lung and liver rather than to the lymph nodes.

Lymph nodes

Multiple lymph nodes are located along the entire length of the colon, and the presence of cancer at the lymph nodes is an indicator of more advanced cancer. The more lymph nodes the cancer has spread to, the higher the N grading.

Margins

The pathology report will also note whether or not the margins are negative for malignancy. The margin is where the surgeon or endoscopist cut to get the tissue out. In most colon cancer surgeries, the surgeon is able to give wide margins to ensure that the tumor has been completely removed. The main exception is in rectal adenocarcinomas where it can be more difficult to remove the entire tumor. In polyps which contain cancers, a negative resection margin is an important factor in determining if further treatment is necessary.

Your pathology report may also contain additional information about genetic tests done on your tissue samples. These may include testing for genetic markers that predispose you to colorectal cancer, or the presence of specific biomarkers that may preclude certain treatments from being effective compared to others.

It may take time to digest and fully understand your pathology report. However, always remember that your doctors are there to walk you through the process and help you make informed decisions about the treatments to move forward with.