Surgical or endoscopic management of malignant colon polyps.

Background: To evaluate indications for colectomy in T1 polyps and possible risk factors for lymph node metastasis.

Methods: Between 2004 and 2017, 40 patients underwent colectomy after endoscopic removal of malignant polyps with T1 carcinoma. Resection was done based on at least one of the unfavourable histopathological criteria. We collected and prospectively studied histopathologic features, short-term results and the benefit-risk balance. Complications were assessed by Clavien-Dindo classification.

Results: Twenty-five patients (62.5%) underwent laparoscopic bowel resection. Twenty-nine patients (63.0%) had more than two unfavourable criteria in the polyp that justified colorectal resection. Thirty-five patients (76%) had G2 (moderately differentiated) cancer, 11 (24%) had G1 (well-differentiated). Five patients (12.5%) had lymph node metastases and one (2.5%) had residual adenocarcinoma. All five patients with lymph node metastasis had G2 cancer. Nine patients (22.5%) had residual adenoma. Overall complications were identified in six (15.0%) patients. Oncologic benefit (or risk factors for lymph node metastasis) was significantly associated with polyp size ≥18 mm (P = 0.006), lymphovascular invasion (P = 0.05) and budding (P = 0.02).

Conclusions: Female gender, lymphovascular invasion, desmoplastic reaction, criteria for surgery ≥2 and polyp size ≥18 mm were all in complex significant risk factors for lymph node metastasis in T1 colorectal cancer. Acting as a single factor, these variables had no effect to increased risk of metastasis.