A colonoscopy is a powerful medical procedure used to visually inspect the entire lining of the colon using a flexible tube equipped with a camera. While it is a frequent occurrence, a biopsy is not always taken during a colonoscopy. Tissue samples are only collected when the physician observes findings that require further microscopic analysis.
When Biopsies Are Necessary
The decision to take a tissue sample is based on specific visual findings or a medical need to investigate symptoms not explained by the colon’s visual appearance. The primary reason for a biopsy is the presence of polyps, which are growths on the colon lining. These polyps are typically removed entirely during the procedure—a process called a polypectomy—and the tissue is sent for analysis to determine its nature.
Polyps are categorized as either adenomatous or hyperplastic. Adenomatous polyps are considered precancerous, meaning they have the potential to develop into colorectal cancer over time if left untreated. Hyperplastic polyps are typically benign and carry a very low risk of becoming malignant, but they are still analyzed to ensure correct classification.
Biopsies are also taken to diagnose or monitor inflammatory conditions of the bowel, such as Ulcerative Colitis or Crohn’s Disease (Inflammatory Bowel Disease or IBD). These conditions cause changes in the colon lining that require microscopic examination for definitive diagnosis and staging. Furthermore, a physician may take small, random tissue samples even if the colon lining appears normal, especially in patients with chronic watery diarrhea, to look for microscopic colitis. This condition involves inflammation only visible under a microscope.
Understanding the Tissue Sample Process
When a tissue sample is needed, the physician uses specialized instruments passed through the channel of the colonoscope. For polyp removal, a wire loop called a snare is often used to cut the tissue and apply an electrical current for cauterization. For smaller or flatter areas of concern, tiny biopsy forceps are used to pinch off a small piece of the lining.
The removed tissue is immediately placed into a labeled container filled with a chemical solution, typically 10% formalin. This solution acts as a fixative, preserving the cellular structure and preventing it from degrading during transport to the lab. Each sample is meticulously documented with the patient’s information and the exact location within the colon from which it was taken.
The samples are sent to a pathology laboratory, where a specialized doctor, known as a pathologist, takes over. The pathologist processes the tissue by embedding it in paraffin wax, slicing it into thin sections, and staining it with special dyes. These steps allow the pathologist to examine the cellular architecture under a high-powered microscope to provide a final diagnosis.
Interpreting the Results
Most patients can expect to wait between three to seven business days for the final pathology report. If the tissue requires special stains or additional molecular testing, the waiting period may extend up to two weeks. The physician who performed the colonoscopy reviews the comprehensive report and discusses the findings with the patient.
The pathology report classifies the tissue into three main categories. A benign result means the cells are non-cancerous and appear normal, requiring no immediate follow-up beyond standard screening. A precancerous result, such as an adenoma or dysplasia, indicates abnormal cell growth that has not yet become malignant.
The most concerning outcome is a malignant result, which confirms the presence of cancer cells. The pathologist’s report provides details on the type and grade of the cancer, which helps determine the necessary treatment plan. The specific findings of the biopsy, such as the number and type of removed adenomas, directly influence the patient’s future surveillance schedule. For instance, findings of multiple or high-risk adenomas often lead to a recommendation for a repeat colonoscopy in three years, rather than the standard five-to-ten-year interval.