摘要Background In both the seventh edition of the International Union Against Cancer (UICC) staging system for gastric cancer and the 14th edition of the Japanese Gastric Cancer Association (JGCA) system,T4a is defined as "Tumor perforates serosa (visceral peritoneum) without invasion of adjacent structures." The aim of this study was to investigate the differences in prognosis between patients with serosa-penetrating and serosa-invading T4aN0M0 gastric carcinomas.Methods Data were collected from 221 patients with T4aN0M0 gastric carcinoma who underwent D2 resection at our cancer center between January 1990 and December 2008.The cohort included 42 patients with serosa-penetratingtumors and 179 patients with serosa-invading tumors.The average follow-up time was 85.5 months.Spearman's rank correlation,Kaplan-Meier plots,and Cox proportional hazards regression models were used to analyze the data.Results The 5-year survival rate of patients with serosa-penetrating and serosa-invading gastric cancers were 31％and 62％ respectively (P ＜0.05).The relapse rates after D2 radical surgery were 16.2％ in patients with serosa-invading gastric cancer versus 59.5％ in those with serosa-penetrating tumors (P ＜0.05).Peritoneal dissemination and distant organ/lymph node metastatic rates were 76.0％ and 24.0％ respectively in patients with penetrating tumors,versus 44.8％and 55.2％ respectively in patients with invading tumors (P ＜0.05).Multivariate analysis showed that penetration of the serosa was an independent prognostic indicator of overall survival.Conclusions Our findings provide a basis for the concept that serosa-penetrating T4aN0M0 gastric carcinoma represents a more aggressive cancer than serosa-invading T4aN0M0 gastric carcinoma.Serosa penetration is an independent factor for poor prognosis of patients with gastric carcinoma.