Clinicopathologic Analysis of Mesorectal Spread of Rectal Cancer with Whole Mount Section

Abstract

Purpose: Total mesorectal excision (TME) has been widely accepted as the principal method in rectal cancer surgery and demonstrates good oncologic and functional outcome. The recurrence rate of mid-low rectal cancer surgery with TME is reported as 5∼6%. Concerning local recurrence, remaining microscopic nodules in mesorectum are a major issue. In this study, we investigated mesorectal spread of tumors and exact lateral resection margin using whole mount section (WMS) to obtain correlations with other clinico-pathological variables. Methods: 63 rectal cancer patients underwent surgery with TME and WMS at National Health Insurance Corporation Ilsan Hospital between December 2005 and October 2008. Preoperative study was made by computed tomography (CT), magnetic resonance imaging (MRI). We measured the distance from the largest cut section of the primary tumor to the nearest circumferential margin using MRI and compared them to lateral resection margins in WMS. Results: Among 63 patients, the sex ratio was 1：1.17 and the median age was 62.7 years. There were 34 patients in TNM stage Ⅲ (54.0%), 21 patients in stage Ⅱ (33.3%) and 8 patients in stage Ⅰ (12.7%). Lateral margin involvement was predicted in 4 cases pre-operatively and confirmed in 3 cases with WMS. Micrometastasis in mesorectum was detected in 6 patients (9.5%) and all were in stage Ⅲ. N stage was statistically correlated with micrometastasis (P=0.016). Conclusion: WMS offers precise lateral resection margin and mesorectal spread of microscopic tumor nodules. WMS is best considered in stage Ⅲ cancer to evaluate mesorectal micrometastasis. The mid-low rectal cancer cases with predicted lateral margin involvements using MRI should be operated on with great care.