Skip lymph node metastasis in gastric cancer: is it skipping or skipped?

Skip metastasis is the presence of a metastatic lymph node (LN) in an extraperigastric (EP) area without perigastric (PG) involvement. The mechanism and prognosis of skip metastasis are still unknown. The purpose of this study was to scrutinize the clinical significance of skip metastasis in gastric cancer.

Data were reviewed from 6,025 patients who had undergone gastrectomy for primary gastric cancer. Patients were categorized as a PG-only group when the metastatic LNs were limited to only the PG area, as a PG + EP group if metastatic LNs extended to both the PG area and the EP area, and as a skip group if metastatic LNs were in the EP area but there were no metastatic LNs in the PG area.

After we had performed matching, the prognosis of the skip group was worse than that of the PG-only group (adjusted hazard ratio 1.69, 95% confidence interval 1.13-2.54) and was similar to that of the PG + EP group (adjusted hazard ratio: 1.54, 95% confidence interval 0.92-2.59). The number of retrieved LNs was less in the skip group than in the other groups, especially from the PG area (p < 0.001).

The prognosis of the skip group was worse than that of the PG-only group and was similar to that of the PG + EP group when the tumor stage was considered. It is difficult to conclude whether skip metastasis is real skipping of cancer cells or a result of inadequate LN sampling. Further evaluation of LNs in the PG area of the skip group could provide more clues for the mechanism of skip metastasis.