Magnetic resonance imaging-detected lymph nodes close to the mesorectal fascia are rarely a cause of margin involvement after total mesorectal excision

Background: In rectal cancer the management of suspicious magnetic resonance imaging (MRI)-detected lymph nodes lying close to the mesorectal fascia poses an ongoing dilemma. Key decisions in treatment planning are commonly based on the prediction of margin status. However, it is unclear whether a lymph node that appears to contain tumour close to the mesorectal fascia will result in a positive margin.

Methods: Some 396 patients with rectal cancer were included. MRI assessment of mesorectal nodes, the pathologically involved circumferential resection margin (CRM) rate and causes of margin involvement were analysed to establish the clinical significance of MRI-detected suspicious lymph nodes at the resection margin.

Results: Fifty (12.6 per cent) of 396 patients had a positive CRM on histopathological analysis, five (10 per cent) solely due to an involved lymph node. Four of the five malignant nodes were not predicted on MRI. Thirty-one of the 396 MRI studies had suspicious nodes 1 mm or less from the CRM. None of these patients had a positive CRM owing to nodal involvement.

Conclusion: Involvement of the CRM by lymph node metastases alone is uncommon.