Re-examining the 1-mm margin and submucosal depth of invasion: a review of 216 malignant colorectal polyps

Malignant colorectal polyps have a risk of lymph node metastases between 9 and 24%, but patients who are negative for certain histologic poor prognostic factors have the potential to be treated with polypectomy alone. Retrospective cohort of 216 malignant polyps from 213 patients identified through the British Columbia Colon Screening Program. Complete pathologic reporting (reporting of tumor grade, lymphovascular invasion, margin status, and tumor budding) was present in only 43% of patients. Sixty-one patients had no poor prognostic factors on polypectomy, and 23 (37%) of those underwent surgery. A positive margin cutoff of tumor at cautery showed significantly increased rates of lymph node metastases (p = 0.04) compared to a margin of greater than 0 mm, and polyps with a margin of greater than 0 mm had no risk of residual carcinoma. A submucosal depth of ≥ 2000 μm had an increased rate of lymph node metastases compared to < 2000 μm (p = 0.01). Malignant polyps with either tumor at cautery or a submucosal depth of ≥ 2000 μm, compared to polyps without these risk factors, had a relative risk for lymph node metastases of 16.3. Adoption of submucosal depth and refinement of the cutoffs for positive margin and submucosal depth have the potential to identify high-risk patients and reduce the number of surgeries required in patients with malignant polyps, a group that continues to grow significantly in part due to the introduction of colon screening programs.