A colonoscopy is a medical procedure used to examine the inner lining of the large intestine and rectum, primarily serving as a screening tool to prevent colorectal cancer. A “positive” result means the physician identified an irregularity, lesion, or growth within the colon that requires closer examination. This finding is common and does not automatically equate to a cancer diagnosis. Instead, it indicates that tissue was removed for laboratory classification. The procedure’s goal is to detect and remove these abnormalities early, preventing them from developing into a malignancy, which dictates the subsequent steps for patient care and monitoring.
Understanding Abnormal Findings
The most frequent abnormality discovered during a colonoscopy is a polyp, a clump of cells forming on the lining of the colon or rectum. These growths are described by their shape and size before being sent to the lab for microscopic analysis. Understanding the physical appearance helps the endoscopist determine the best method for removal during the procedure (polypectomy).
Polyps are generally classified into two main structural forms: pedunculated and sessile. Pedunculated polyps resemble a mushroom, growing on a distinct, narrow stalk, which often makes them easier to remove. Sessile polyps are flat or slightly raised, attaching directly to the colon wall with a broad base, and their removal can be more technically demanding. Larger growths, typically those one centimeter or greater in diameter, are associated with a higher potential for advanced cellular changes.
The physician removes these lesions using specialized tools passed through the colonoscope, such as a wire loop (snare) or biopsy forceps. Complete removal of the abnormal tissue is generally achieved during the colonoscopy itself, which acts as both a diagnostic and therapeutic tool. Once removed, the tissue is collected and sent to a pathologist, who analyzes the cells to determine the precise nature and risk level of the finding.
Decoding the Pathology Report
The pathology report provides the definitive classification of the removed tissue, which determines future medical management. The report differentiates findings into non-precancerous, precancerous, and malignant categories based on the microscopic appearance of the cells. The majority of polyps are non-precancerous, such as hyperplastic polyps, which are common and carry virtually no risk of developing into cancer.
Precancerous lesions, known as adenomas, are the most common and important findings because they are precursors to most colorectal cancers. Adenomas are classified by their cellular architecture, with tubular adenomas posing the lowest risk of progression. Villous adenomas and tubulovillous adenomas carry a progressively higher risk. Sessile serrated lesions (SSLs) are another type of precancerous polyp that are often flat and have a significant potential for malignant transformation.
The report also specifies the degree of cellular abnormality, termed dysplasia, noting if it is low-grade or high-grade. High-grade dysplasia indicates that the cells are very abnormal and closely resemble cancer cells, signifying a more advanced precancerous stage. The difference between a precancerous adenoma and a true cancer is the presence of invasion. A diagnosis of invasive cancer is made only when the malignant cells have broken through the basement membrane and spread into the deeper layers of the colon wall.
Immediate and Long-Term Surveillance
Following the pathology report, the next step involves establishing an individualized surveillance plan to monitor the colon for new growths. This plan depends entirely on the characteristics of the polyps that were removed. Patients are stratified into different risk groups based on the number, size, and type of adenomas found.
If findings are considered low-risk—typically one or two small tubular adenomas with low-grade dysplasia—the follow-up colonoscopy is often scheduled for five to ten years later. This longer interval reflects the low likelihood of developing new, advanced lesions. Conversely, a high-risk finding requires a much shorter surveillance interval, usually three years after the initial polypectomy.
High-risk characteristics require accelerated surveillance to identify and remove recurring precancerous polyps quickly. These characteristics include:
- Three or more adenomas.
- Any adenoma measuring one centimeter or larger.
- Any adenoma with villous features or high-grade dysplasia.
- A sessile serrated lesion one centimeter or larger.
- A sessile serrated lesion with any degree of dysplasia.
Implications of a Cancer Diagnosis
When the pathology report confirms invasive colorectal cancer, the focus shifts from prevention to active disease management. The first steps involve additional tests to determine the extent of the cancer’s spread, a process known as staging. Imaging procedures, such as computed tomography (CT) scans, are commonly performed to check if the cancer has spread to distant organs or nearby lymph nodes.
The cancer is classified using the TNM staging system, which assesses the size of the original tumor (T), spread to nearby lymph nodes (N), and metastasis to distant sites (M). Staging guides the treatment strategy. Early-stage cancers (Stage I) are often treated with surgery alone, while more advanced stages (Stage II-IV) generally require a combination of therapies.
Treatment modalities typically include surgery to remove the cancerous section of the colon and surrounding lymph nodes, often followed by chemotherapy. For cancers located in the rectum, radiation therapy may be used in addition to chemotherapy and surgery. The entire process is managed by a multidisciplinary team of specialists, including medical, surgical, and radiation oncologists, who collaborate to create a personalized treatment plan.