Rectal adenocarcinoma: assessment of tumour involvement of the lateral resection margin by MRI of resected specimen

The aim of the present study was to investigate whether MRI could predict t umour involvement of the lateral resection margin on resected rectal cancer specimens. 26 specimens obtained after total mesorectal excision were exam ined in the sagittal and axial plane on a clinical 1.5 T MR system using ph ased-array surface coils. The shortest distance between the deepest point o f tumour penetration and the lateral resection margin was measured. This di stance is referred to as LRM. The results were correlated to measurements o n digital images of giant histopathological sections. The total number of l ymph nodes and lymph node metastases was also counted. LRM was less than or equal to 1 mm (a distance considered for non-radically excised tumours) in eight of the histopathological specimens. On MR images of the resected spe cimen. LRM was less than or equal to 1 mm in seven of these specimens. LRM was shorter in MR examinations than in histopathological giant sections in Il specimens. The sensitivity, specificity, positive and negative predictiv e values for prediction of tumour involvement of the lateral resection marg in (LRM less than or equal to I mm) by MR of the resected specimen were 88% , 78%, 64% and 93'%,, respectively. Presence of lymph node metastases could not accurately be predicted by MR. However, it is concluded that the prese nce of a tumour free lateral resection margin can be predicted by MRI of re sected rectal specimens when this exceeds 1 mm.