A colonoscopy is a standard medical procedure used to examine the large intestine for abnormalities, most commonly as a screening tool for colorectal cancer. During this examination, the physician routinely identifies and removes growths on the colon lining called polyps. The discovery of a polyp is frequent, but finding that one contains cancerous cells means the initial diagnosis is complete, and a focused treatment path begins immediately. This transitions the patient from routine screening to a specific oncology follow-up plan.
Pathology: Confirming the Cancer Diagnosis
After removal, the polyp is sent to a laboratory for analysis by a pathologist. This expert determines if the growth is a benign adenoma or an adenocarcinoma (true cancer). The pathology report confirms the presence of cancer cells and provides crucial details about their behavior.
The report distinguishes between non-invasive and invasive cancer. Non-invasive cancer (carcinoma in situ, or Tis) means the malignant cells are confined entirely to the inner lining of the colon. Invasive cancer has penetrated past the muscularis mucosa, the thin muscle layer separating the inner lining from the submucosa below. This invasion classifies the growth as a true malignant polyp and creates a risk of spread to lymph nodes.
The pathologist also assesses high-risk features that dictate next steps, such as the cancer grade and the status of the resection margin. A poorly differentiated, or high-grade, tumor looks very abnormal and tends to grow more aggressively. The margin status indicates whether cancer cells extended to the edge of the tissue removed, suggesting that some cancerous tissue may remain in the colon wall.
Immediate Next Steps: Removal or Referral for Surgery
The pathology report determines if the initial polypectomy was curative or if more aggressive treatment is necessary. If the cancer was non-invasive or a small, invasive polyp with favorable features, the polypectomy may be considered definitive treatment. Favorable features include a well-differentiated tumor grade, no evidence of cancer cells in the blood or lymph vessels (lymphovascular invasion), and clear margins (ideally more than one millimeter from the edge of the removed tissue).
If the cancer was large, had poorly differentiated cells, or showed lymphovascular invasion, a surgical consultation is required due to the increased risk of residual disease or lymph node metastasis. The recommended procedure is a segmental resection, or colectomy. This operation involves surgically removing the section of the colon where the polyp was found, along with nearby lymph nodes, to ensure complete cancer clearance.
For a malignant polyp, the endoscopist tattoos the site during the colonoscopy with a small injection of dye to mark its exact location. This tattooing is performed slightly away from the lesion to guide the surgeon accurately to the correct segment of the colon. This step helps obtain a clear margin and fully stage the cancer by examining the lymph nodes for microscopic spread.
Cancer Staging and Systemic Treatment Decisions
Following the definitive removal of the cancer, the next major step is staging, which determines if the cancer has spread beyond the colon wall. Staging uses the Tumor, Node, Metastasis (TNM) system, evaluating the depth of the primary tumor (T), the involvement of nearby lymph nodes (N), and the presence of distant spread (M). Localized cancer confined to the colon wall is a lower stage, while spread to lymph nodes or distant organs results in a higher stage designation.
A full workup involves follow-up tests such as computed tomography (CT) scans of the chest, abdomen, and pelvis to look for distant metastases. Blood tests, specifically the marker Carcinoembryonic Antigen (CEA), are also checked. While not a diagnostic tool, CEA monitors the cancer’s response to treatment and detects later recurrence. The results of the lymph node analysis and imaging scans determine the final stage.
The cancer stage guides decisions about additional, or systemic, treatment. For the earliest stages (Stage 0 or Stage I), where the cancer is confined and fully removed, no further treatment beyond monitoring is typically needed. If the cancer is Stage II or Stage III, meaning it has invaded deeper or spread to nearby lymph nodes, the medical oncologist may recommend adjuvant therapy. This generally involves chemotherapy, and sometimes radiation, administered after surgery to eliminate microscopic cancer cells.
Long-Term Surveillance and Recovery
The long-term management plan focuses on recovery and rigorous surveillance to detect cancer recurrence or the development of new polyps. The risk of developing another cancer persists even after successful initial treatment. Patients who have had a cancerous polyp removed are considered high-risk and require more frequent check-ups than the general population.
Surveillance colonoscopies are performed to clear the colon and monitor for new growths. A follow-up, or clearance, colonoscopy is generally recommended within one year of the initial cancer removal. Subsequent surveillance colonoscopies are typically scheduled three years after the clearance scope, and then every five years if no high-risk polyps are detected.
In addition to endoscopic monitoring, patients have regular visits with their oncology team, often including ongoing blood tests to monitor CEA levels. Lifestyle adjustments, such as maintaining a healthy weight, adopting a diet rich in fruits and vegetables, and engaging in regular physical activity, are encouraged to promote overall health and reduce the risk of future cancer development.