Understanding Your Pathology Report: Adenomas and Adenocarcinomas

In the course of investigating any symptoms you are experiencing that might be indicative of colorectal cancer, you may be required to undergo a colonoscopy, a visual examination that helps doctors check your colon for any growths that are potentially cancerous.

Sometimes, these growths can be removed during the colonoscopy and be sent for laboratory testing to determine the likelihood of developing into a tumor — this procedure is referred to as a biopsy. Following the biopsy, you would be given a biopsy or pathology report detailing the outcome of the laboratory test, of which the results are used to determine your diagnosis

Your pathology report will contain many scientific and medical descriptions which may be difficult to understand. This series of articles covers specific findings and their related diagnoses, which we hope helps you prepare for any discussions with your healthcare providers. In this article, we discuss what it means when adenomas or adenocarcinomas have been identified in your pathology report.

Adenomas, an alternative name for adenomatous polyps, are neoplastic polyps made of tissue that resemble the colon’s inner lining, and any differences from the colon’s lining needs to be distinguished under a microscope.

Adenomas can be further classified into two different growth patterns: tubular or villous patterns. Your pathology report may report their appearance as one of the following:

• Tubular adenoma
• Tubulovillous adenoma
• Villous adenoma
• Sessile serrated adenoma (sessile serrated polyp)
• Traditional serrated adenoma

Adenomas are considered precancerous growths — they do not contain any cancer yet, but have a high likelihood of developing further into cancer if left alone to grow. How likely an adenoma (or any polyp, for that matter) will develop into cancer can be observed through how much dysplasia is observed.

Dysplasia is used to describe abnormal cellular growth such that the cell’s appearance is different from normal. Dysplasia can be either low-grade or high-grade.

Low-grade dysplasia: The cells appear only slightly abnormal and for the most part resemble a normal functioning cell. These are considered mild cases and are not usually a cause for concern.

High-grade dysplasia: The cells appear more abnormal and unlike a normal functioning cell. These cells are more likely to be cancerous. Cells that exhibit high-grade dysplasia are poorly differentiated and bear little resemblance to healthy cells in the surrounding tissue.

Sessile serrated adenoma/polyp/lesion polyps do not always show the cellular changes that pathologists diagnose as dysplasia; reports on these cases will therefore say whether or not there is dysplasia present. If it is present, the pathologist will note whether it is low or high grade. Even with the absence of the diagnosis of dysplasia, these lesions are still considered to be precancerous growths.

Adenocarcinomas, which makes up 96% of colorectal cancer cases, are caused when cancer develops on the inner lining of the colon. More specifically, ‘adeno’ refers to glands, while ‘carcinoma’ refers to a cancer that arises in the epithelial tissue or lining of an organ.

The inner lining of the colon is made up of cells that secrete mucus to help maintain a healthy relationship between the epithelial lining and gut bacteria. By forming a protective layer, the mucus inhibits infection and prevents inflammation.

Adenocarcinomas begin in these glandular cells, forming small polyps that can continue to grow into malignant tumors.

Early adenocarcinomas and adenomas may not be immediately diagnosed as ‘cancer’ despite their growth patterns suggesting otherwise. Until a lesion has been identified as being able to spread, it is usually considered a pre-cancer. You may also know this by other names, including cancer in situ, or stage 0 cancer.

Infiltrating or invasive adenocarcinomas, on the other hand, indicate that the cancer is able to “travel” or metastasize from the point of origin to other parts of the body. This includes growing through the intestine’s different layers, spreading to the nearby lymph nodes, or in more severe cases, spreading to other organs such as the lung and liver.

If cancer has been identified, the samples extracted during the colonoscopy or surgery are also tested for different biomarkers. These biomarker tests will help identify which genetic mutations are causing the cancerous growth, and is an important step as it also helps to determine which treatments (such as immunotherapies or targeted therapies) will be more effective compared to others. The biomarker tests that are conducted may include:

● Changes in the KRAS, NRAS, and BRAF genes

● Changes in mismatch repair (MMR) genes, such as MLH1, MSH2, MSH6, and PMS2

● The level of microsatellite instability (MSI) in the cancer cells

● The level of tumor mutational burden (TMB)

● Levels of the HER2 gene or protein

● Changes in the NTRK genes

Biomarker testing may also help identify any inherited mutations, particularly those in mismatch repair genes or high microsatellite instability. While these are ‘trademark’ mutations in individuals with Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC), they may also occur in patients without any underlying syndromes. If felt to be a hereditary syndrome, this may prompt further genetic testing amongst your direct relatives, as they are at an elevated risk of colorectal cancer if they carry these mutations.

In this article, we identified the differences between adenomas and adenocarcinomas, along with how they relate to your cancer stage and diagnosis. Your pathology report may contain your diagnosis, which will help your medical team recommend the best treatment plan for your condition moving forward. In cases where further tests are required, your team of doctors will be able to advise the next steps as well as guide you through the process.