Ignoring small lymph nodes can be a major cause of staging error in gastric cancer

Stage migration in gastric cancer confounds establishment of standard treatment according to stage.

To determine how closely lymph nodes should be examined to report correct staging, 402 node-positive patients were evaluated retrospectively. A total of 23,233 lymph nodes were reviewed histologically and their maximum dimension was measured. Another 254 nodes from 12 patients were used to evaluate shrinkage after fixation and preparation of the histological slide.

Metastasis was detected in 3142 nodes, 1163 with well differentiated tumours (WDTs) and 1979 with poorly differentiated tumours (PDTs). Mean(s.d.) size of metastatic nodes was 7.80(5.08) mm in all, 8.44(5.74) mm in WDTs and 7.42(4.62) mm in PDTs. Both positive and negative nodes shrank between 10 and 20 per cent during histological processing. If all nodes 5 mm or less in size when fixed are ignored 37.8 per cent of all metastatic nodes will be missed. Downstaging will occur in 14.9 per cent and 4.2 per cent of the cases if all nodes less than 6 and 4 mm respectively are ignored.

To keep the rate of stage migration caused by this factor below 5 per cent, all lymph nodes 4 mm or more in size (5 mm when fresh) should be retrieved and examined.