RESUMO
OBJECTIVE: To estimate the number of lymph nodes(LNs)needed to be examined for adequate LN staging via nodal staging score(NSS).METHODS: A model was fitted based on 3989 pN + patients with resected primary pancreatic adenocarcinoma in the Surveillance,Epidemiology and End RESULTS:(SEER)database.The number of nodes to examine to achieve an N SS of 90% was used as the optimal number.The results were validated in node negative patients from the SEER cohort(2583 patients)and a local multicenter cohort(93 patients).RESULTS: Tumor size is a determinant for the extent of lymphadenectomy.According to the tumor size<2 cm and ≥2 cm,15 and 20 LNs would need to be examined to achieve90% confidence in a pN0 patient.As a result of missing node-positive case,the prevalence of nodepositive was adjusted from 60.7% to 71.0%.In the survival analysis,more LNs examined was shown to be correlated with better prognosis in patients with tumor ≥2 cm.CONCLUSION: The minimum number of LNs for adequate staging depends on the tumor size.The estimation provides a practical standard for evaluating the extent of LN yield for surgeons.