To examine factors that influence lymph node count and to study the relationship between nodal size and metastatic involvement in gastric cancer.Methods and results:
Observational study comparing lymph node retrieval by manual nodal dissection (MND) and systematic fat blocking (SFB) from 114 gastrectomy specimens. The influence of lymph node retrieval method, patient characteristics, oncological factors and surgical approach on lymph node count were examined using regression models. The risk-adjusted cumulative sum chart method was also used to analyse lymph node count. The lymph node count increased during the course of this study (P < 0.005). Both pathologist and lymph node retrieval method were independent predictors for lymph node count. MND yielded lower lymph node counts than SFB (58 versus 66, P < 0.05). The pathologist influenced lymph node retrieval by MND (R2: 0.297–0.518, P < 0.0001), but not SFB (R2: 0.340–0.344, P > 0.05). The percentage of positive lymph nodes below 5 mm was 24.2% and 44.1% for MND and SFB, respectively, resulting in cancer upstaging (P = 0.037).Conclusions:
Systematic fat blocking is associated with a higher total and positive lymph node yield compared to MND and is independent of the pathologist. Ignoring small lymph nodes can be a major cause for missing positive nodes, leading in turn to cancer down-staging.