A biopsy is the only sure way to find out if an abnormality in the colon or rectum is cancerous. During a colonoscopy, a surgeon or gastroenterologist removes a sample of suspicious tissue. This tissue is examined by a pathologist using a microscope, who will then diagnose whether the cancer is benign or malignant. Sometimes the abnormal cancer polyp is removed by polypectomy alone (dependent on the size of the polyp) or if appropriate after confirmation of cancer by biopsy, the surgeon will remove the segment of colon or rectum where the tumor is located. If the tumor is in the rectum, it is likely you will receive chemotherapy combined with radiation therapy before the surgical resection. The excised tumor is then examined by a pathologist, who sends a pathology report to the physician.
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The pathology report includes both a macroscopic and microscopic description. The macroscopic report is a description of the physical characteristics, such as the color and size, of the biopsy sample. It also provides a description of the tumor, including color, appearance, size, and distance from the surgical margins in a resection specimen. The microscopic evaluation describes the appearance of the cells under a microscope, and includes the tumor grade, depth of invasion, margin status, and lymph node involvement. The pathologist uses the information in the microscopic report to help determine the stage of the cancer.
A pathology report is written in medical language and the technical wording on it can sometimes be very confusing. This guide will help you better understand the report and your diagnosis. Here is the information you may see on your pathology report:
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Tumor type describes the type of cell the cancer originally formed in. Over 95% of colon and rectal cancers are adenocarcinomas, meaning they form in the glandular cells that line the inner layer of the large intestine. If your surgeon removed any polyps during your colonoscopy, this section will also describe the polyp type. Specific types of polyps are more likely to become cancerous than others.
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Your doctor will measure the size of a tumor at its widest point. The standard unit of measurement is centimeters (cm). Tumor size is important in determining if a polyp is cancerous or if tumor is more likely to be higher stage.
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Grade describes how different the cancer cells are compared to normal cells. Experts examine these cells under a microscope and compare their appearance and behavior to determine the grade.
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Your surgeon will remove an extra area of normal tissue around your tumor to be sure the cancer is completely removed. This incisions made in the colon or rectum by the surgeon are called the margins of resection. The lab measures the distance from the cancer to the outer edges of the tissue and places the results in the pathology report.
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Some tumors are non-invasive or "in-situ," meaning they are confined to colonic or rectal mucosa (surface) and have not invaded the colonic or rectal wall. Invasive tumors grow into the colonic or rectal wall and surrounding healthy tissue and can potentially spread throughout the body. The pathologist will include information on the extent of invasion in the colon or rectum wall in the pathology report. For example, the pathology report will tell you whether your cancer has grown completely through the outer wall, if it has grown through to the outer layer, but has not yet breached the wall, or if it is still located only in the inner layer.
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The pathologist will examine the blood and lymph vessels in the biopsy sample to see if any cancer cells have invaded them. When cancer cells invade these vessels, it is called a lymphovascular invasion, and is a sign of an aggressive tumor with metastasis (spread of tumor to other sites) to lymph nodes and other organs such as liver.
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The lymph nodes are responsible for filtering waste products from the blood before it circulates back to the rest of the body. If your lymph nodes contain abnormal cells, there is a high risk the cancer could spread to the rest of your body. Your pathology report will contain information about the status of your lymph nodes.
Here are some questions you could ask your doctor to help you better understand your pathology report:
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