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

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.

Accuracy of Magnetic Resonance Imaging in Predicting TNM Staging and Circumferential Resection Margin Compared with Pathologic Assessment on Whole-mount Section in Rectal Cancer

PURPOSE: Recently, magnetic resonance imaging (MRI) has become the preferred diagnostic tool for preoperative assessment of TNM staging and circumferential resection margin (CRM) in patients with rectal cancer. The aim of this study is to evaluate the accuracy of preoperative MR imaging in the prediction of T, N stage and CRM compared with pathologic results on whole- mount sections. METHODS: Thirty-five consecutive patients with rectal cancer were enrolled between Dec. 2005 and Apr. 2006. 1.5-T MR imaging, was performed, and pathologic results were investigated on whole-mount sections. The agreement between MR imaging and pathologic examination for the assessment of T, N stage and status of CRM were analyzed using kappa statistics. RESULTS: The accuracy of MR imaging compared with pathologic assessment of T stage was 82.9% (kappa=0.56), and that of N stage was 74.3% (kappa= 0.31). Of the MR imaging planes, the oblique axial plane showed the most accurate prediction of CRM, regardless of tumor position within the circumference of the rectum. The accuracy of MR imaging in the oblique axial plane for predicting the CRM was 81.0% (kappa=0.62) in anterior and posterior rectal tumors and 71.4% (kappa=0.43) in laterally located rectal tumors. With a different CRM criteria for the measured distance in MR imaging, the accuracy of the 2-mm CRM criterion was 77.1% (kappa=0.53). CONCLUSIONS: MR imaging in predicting T stage showed fair agreement according to kappa statistics. Of the MR imaging planes, the oblique axial plane provided the most accurate CRM information compared with pathologic examination. The actual measured distance of the CRM in MR imaging can be applied to the pathologic CRM.