Management of Completely Resected Malignant Sigmoid Polyp with Favorable Features
Observation is the recommended next step for this patient, as the polyp meets all criteria for favorable histology: well-differentiated adenocarcinoma (grade 1-2), clear margins, no lymphovascular invasion, and no muscularis propria involvement. 1
Rationale for Observation
The National Comprehensive Cancer Network (NCCN) guidelines explicitly state that no additional surgery is required if the polyp has been completely resected and has favorable histologic features, which include:
- Grade 1 or 2 differentiation (well or moderately differentiated) 1
- No angiolymphatic invasion 1
- Negative resection margins 1
Your patient's polyp meets all three criteria with well-differentiated adenocarcinoma, free margins, and no documented lymphovascular invasion.
Risk of Residual Disease
The evidence supporting observation is compelling. A comprehensive analysis of 16 studies involving 412 patients with malignant polyps showed that only 13.3% had residual disease, positive lymph nodes, or recurrence—and the vast majority of these adverse outcomes occurred in patients with unfavorable histologic features. 1 When favorable features are present, as in your patient, the risk of residual disease is substantially lower.
Critical Distinction: Pedunculated vs. Sessile Polyps
One important caveat: The NCCN guidelines note that sessile polyps with favorable features may warrant consideration of colectomy as an option (in addition to observation) because sessile polyps have a significantly higher incidence of adverse outcomes compared to pedunculated polyps, likely due to higher probability of positive margins after endoscopic removal. 1 However, since your patient has documented clear margins, this concern is mitigated.
Essential Follow-Up Requirements
While observation is appropriate, the following steps are mandatory:
- Complete colonoscopy to rule out synchronous polyps 1
- Surveillance colonoscopy at appropriate intervals 1
- No adjuvant chemotherapy is indicated for stage I lesions 1
When Surgery Would Be Indicated
Colectomy with en bloc lymph node removal would be required if any of the following unfavorable features were present:
- Grade 3 or 4 differentiation (poorly differentiated) 1
- Angiolymphatic invasion 1
- Positive or indeterminate margins 1
- Fragmented specimen preventing margin assessment 1
Common Pitfall to Avoid
Do not reflexively recommend surgery based solely on the presence of invasive carcinoma. The key is careful pathologic review of the specific histologic features. 1 Even when unfavorable features are present and surgery is performed, the majority of resection specimens show no residual tumor and negative lymph nodes. 1
Answer: A - Observation