Patterns of lymphatic spread in rectal cancer. A topographical analysis on lymph node metastases.

The presence of lymph node (LN) metastases is the most important prognostic factor in rectal cancer. The exact LN status can only be known when an extended lymph node dissection (LND) has been performed, a process not routinely performed. If the likelihood of LN metastases can be more accurately assessed preoperatively, then an optimal multimodality treatment plan can be established. 605 patients with primary rectal cancer operated upon with wide LND (D3 level) were analysed for LN metastases combining topographical localisation and morphological features of the tumour. More distal rectal tumours tend to more LN metastases and more lateral lymphatic spread. Tumours >or=3 cm show more LN metastases compared with those smaller than 3 cm. Depth of bowel wall invasion is strongly related to the presence of LN metastases. The peritoneal reflection has no discriminating role in the mode of spread. Intra-operative assessment by the surgeon for presence of LN metastases is not reliable. When localisation, depth of bowel wall invasion and diameter of a rectal tumour are known, a likelihood of LN metastases can be assessed pre-operatively, not intra-operatively.