Understanding Your Pathology Report: Colorectal Polyps

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 the types of polyps that may be found in your colon that are extracted for biopsy.

Polyps, or growths, may form in the colon through different ways, and depending on how they grow, this gives rise to different types of polyps. Not all polyps are considered cancerous, so what are the determining factors that lead a pathologist to conclude that the growth has tumorous potential?

• Size of the polyp: Large polyps 10 mm or larger in diameter are considered to have significant risk of developing into cancer.
• The growth pattern: Polyps may have tubular, villous or tubulovillous growth patterns. Villous growth patterns are indications of more chaotic and rapid cell growth.

Size of the polyp

Firstly, size is an important determinant of a polyp’s cancerous potential. A polyp may be described as diminutive, small, large or giant, and the likelihood of each polyp being cancerous can be judged based on its size at the time of discovery.

Diminutive and small polyps are easily removed during a colonoscopy, while large or giant polyps may require removal through surgery. Large and giant polyps have the greatest potential of being cancerous, as colorectal polyps take a long time — 10 years on average — to develop. Nonetheless, this does not mean that smaller polyps do not carry the same risk, as every polyp will start small.

Polyp shapes and growth patterns

The polyps that are removed are tested in a lab to more accurately determine their cancerous potential. Since each polyp may grow in a different manner from others, this also gives rise to different growth patterns and appearances of each polyp, which are also described in detail in your colonoscopy report if they were identified or extracted during a colonoscopy. Its appearance is another way to determine if it is likely to develop into cancer.

For colorectal cancer, we are most concerned with neoplastic polyps — polyps that arise through an autonomous, abnormal cellular growth process known as neoplasia. Cells that make up neoplastic tissue are characterized by a similar genetic makeup that results from cellular transformation or loss of growth regulation, such as deactivation of tumor suppressor genes or overexpression of oncogenes. We are familiar that mutations in these genes have a high tendency to result in cancerous growth.

The morphology — form and structure — of a lesion can be described as polypoid that protrude from the mucosal lining, or non-polypoid that have flat or depressed structures. In general, polyps that form are either pedunculated or sessile, where they appear attached to the lining to a stalk (pedunculated, or resembling a cherry or mushroom) or have a dome shape that lies flat against the wall of the intestine (sessile).

Sessile polyps make up about 85% of all polyps found, and together with pedunculated polyps are typically easy to remove during a colonoscopy.

On the other hand, non-polypoid lesions have flat or superficial forms make up about 2% of discovered lesions and can be flat and elevated, completely flat, superficially depressed or excavated/ulcerated. At times, some non-polypoid lesions may also appear flat and elevated with a central depression.

In addition to its external appearance, polyps can also be differentiated by their appearance under the microscope. Different polyps exhibit different growth patterns based on how they grow, and these growth patterns can also provide hints on how likely and quickly the polyp will grow further.

One of the ways a polyp’s growth pattern can be described is as serrated, where polyps resemble saw teeth.

At this stage, it is important to note that your pathology report may describe the polyps as pedunculated or sessile, and these terms may also be used to describe adenomas, an alternative name for adenomatous polyps. These neoplastic polyps are 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.

Nonetheless, adenomas can be further classified into two different growth patterns: tubular or villous patterns.

While many adenomas have a mixture of both tubular and villous growth patterns (called tubulovillous adenomas), smaller adenomas typically have tubular growth that resemble small tubes packed into the colon lining. Larger adenomas have a villous pattern that looks frond-like; the outward spreading pattern is indicative of rapid and more chaotic growth and a higher likelihood of cancer.

In this article, we discussed several types of polyps, with particular focus on those that are more likely to become cancerous. It’s important to note that growths that have been identified as polyps or adenomas are not tumors, and are instead considered as precancerous lesions.

If these have been identified in your pathology report, follow up with your doctor on further treatment, especially if larger polyps and adenomas have not been completely removed during the colonoscopy.