Risk Factors of Lymph Node Metastasis in Patients with Early Pure and Mixed Signet Ring Cell Gastric Carcinomas

Background: Early gastric carcinoma (EGC) with pure signet ring cell carcinoma (pSRCC) has been reported to have favourable prognosis and low risk of lymph node metastasis (LNM). However, risk factors of LNM and clinicopathological features for early gastric mixed signet ring cell carcinoma (mSRCC) remain poorly investigated. The aim of this study was to identify risk factors of LNM and compare clinicopathological characteristics and prognosis of early gastric pSRCC with mSRCC. Methods: This retrospective study was conducted at our center between 2005 and 2015 in 796 patients underwent radical gastrectomies combined with lymph node dissections, A total of 160 patients with early gastric SRCC underwent gastrectomies with lymph node dissections were reviewed, in which 79 cases were pSRCC and 81 cases were mSRCC. Risk factors of LNM and clinicopathologic features of these two groups were statistically compared, including age, gender, tumor location, gross pattern, size, invasion depth, lymphovascular invasion (LVI), helicobacter pylori (Hp) infection, atrophic gastritis, ulcer finding and LNM. Patients were follow-up for post-resection survival. The 5-year survival and disease-specific survival rate were estimated with the Kaplain-Meier method with a log-rank test and compared between the two groups. Results: Tumor size (P<0.05), invision depth (P<0.05) and LVI (P < 0.0001) were risk factors of LNM, LVI (P < 0.0001) was independent risk factor of LNM in 160 patients. Univariate analysis reviewed LVI (P < 0.0001) as the risk factor in the pSRCC group, and the risk factors of LNM in the mSRCC included LVI (P < 0.0001) and tumor size (P<0.05). Multivariable analysis revealed two independent risk factors in the mSRCC group: 1) tumor size (P < 0.05), and 2) LVI (P < 0.0001). The significant characteristics in two groups included the male gender (P < 0.0001), gross pattern (P < 0.05), LVI (P < 0.01), and Hp infection (P < 0.01). The difference of LNM rate between expanded indication and out of indication in 160 patients was significant (P=0.03). The overall 5-year survival rate for early gastric SRCC was 96.3%. There was no significant difference in the overall survival and disease-specific survival between the two groups. Conclusions: Although with similar post-resection survival, the independent risk factors of LNM in the early mSRCC group, compared to those in the early pSRCC group, included large tumor size and LVI. Early gastric mSRCC had more aggressive clinicopathological features than pSRCC.