Clinicopathologic Analysis of Lateral Margin Measured by Whole-Mount Section in T3 Rectal Cancer

Abstract

Purpose Total mesorectal excision is a standard technique for rectal cancer. The whole-mount section can encompass the entire specimen, so it is a more appropriate for measuring circumferential margin than conventional section. We analyzed the clinical characteristics and prognosis based on lateral margins (LMs) measured by whole-mount sections. Methods Medical records of patients who were operated on for T3 rectal cancer from 2005 to 2015 were reviewed retrospectively. A total of 154 patients were included. The slides of the whole-mount sections were re-reviewed by a single pathologist. Results We divided the groups according to the length of the LM (1 mm, 1.5 mm, and 2 mm). There was significantly frequent lymphovascular invasion and N state was higher when LM was short in all groups. There were more micrometastasis in group LM ≤1 mm (53.3% ≤1 mm vs. 26.6% >1 mm, P=0.039), but not in other groups. When looking at local recurrence alone, there was no significant difference between groups, but the 5-year local recurrence-free survival was significantly worse when LM ≤2 mm (P=0.050). In each analysis based on 1 mm and 1.5 mm, overall survival was worse when LM was short. In all groups, disease-specific survival was worse when LM was short. Conclusion As previously known, securing a margin less than 1 mm negatively affects the prognosis. When LM was divided by 1.5 mm, there was a significant difference in overall survival. There was a significant difference in disease-specific survival when divided by 2 mm in T3 rectal cancer. However, further studies with more patients are necessary to secure the result.

Keywords

• rectal neoplasms
• whole-mount section
• prognosis
• lateral margin
• neoplasm micrometastasis