Method of specimen fixation and pathological dissection of colorectal cancer influences retrieval of lymph nodes and tumour nodal stage

Introduction There is now evidence that meticulous specimen dissection may «upstage» around one-quarter of colorectal cancers from node negative to node positive, although there is much debate as to how to achieve this: some authors prefer fat clearance techniques while others have opted for more conventional lymph-node retrieval with manual specimen «breadknifing» and lymph-node palpation. While fat clearance is probably the optimum technique, it is time-consuming, costly and does not provide rapid diagnostic results. Methods A prospective pathological study of 50 colorectal cancer resections was conducted with 100 comparison cases, the study group receiving at least an additional 24-h fixation of the mesocolonic or mesorectal fat in 10% aqueous formaldehyde prior to specimen dissection.Results The percentage of node-negative colorectal cancer was significantly lower in the study group compared with the matched comparison group: (18) 36% compared with (55) 55% of comparison cases. Conclusions Effective lymph-node retrieval techniques require mesocolic/mesorectal fat to be adequately fixed prior to pathological dissection. This study suggests that satisfactory lymph-node retrieval is possible without fat clearance, provided the mesenteric fat is suitably fixed prior to colorectal cancer specimen dissection.