What are the three pathological findings that indicate the need for operative intervention after a polyp is removed by snare (surgical removal using a wire loop) and found to have cancer?

From the Guidelines

If a polyp removed by snare has cancer, the three key findings on the pathology report that would indicate the need to go to the OR are: poorly differentiated adenocarcinoma, lymphovascular invasion, and positive margins (<1 mm). These findings are based on the most recent and highest quality study by the US Multi-Society Task Force on Colorectal Cancer 1. The importance of these factors lies in their association with an increased risk of lymph node metastasis (LNM) and local recurrence. Key points to consider include:

• Poorly differentiated adenocarcinoma is a high-risk feature associated with LNM, as shown by studies such as Miyachi et al, which found poor differentiation to be a significant predictor of LNM (OR, 2.31; 95% CI, 1.25–4.27) 1.
• Lymphovascular invasion is another critical factor, with a strong independent association with LNM (RR, 5.2; 95% CI, 4.0 – 6.8), as highlighted in the systematic review by Bosch et al 1.
• Positive margins, defined as <1 mm, indicate incomplete removal of the cancer and a high risk of residual disease, making surgical resection necessary to ensure complete removal of the tumor 1. Additional factors that may influence the decision to proceed with surgery include deep submucosal invasion, tumor budding, and the method of polyp removal (piecemeal vs. en bloc resection). However, the three primary indicators of the need for surgical intervention are poorly differentiated adenocarcinoma, lymphovascular invasion, and positive margins (<1 mm), as these are the most strongly associated with an increased risk of LNM and local recurrence 1.

From the Research

Indications for Surgical Intervention

The following are indications that may require surgical intervention after a polyp is removed by snare and found to have cancer:

• Incomplete resection, as indicated by positive margins 2, 3
• High-grade dysplasia or cancer with invasive characteristics 2, 3
• Piecemeal resection, which may increase the risk of local recurrence with malignancy 3

Path Report Findings

The path report may indicate the following findings that would necessitate surgical intervention:

• Positive horizontal or vertical margins, indicating incomplete resection 2
• Presence of invasive cancer or high-grade dysplasia 2, 3
• Residual tumor or adenomatous tissue, indicating incomplete resection 2

Risk Factors for Local Recurrence

The following are risk factors for local recurrence with malignancy after endoscopic resection of large colon polyps with high-grade dysplasia:

• Piecemeal resection 3
• Positive margins 2
• Invasive characteristics of the cancer 2, 3