Histologic purity of signet ring cell carcinoma is a favorable risk factor for lymph node metastasis in poorly cohesive, submucosa-invasive early gastric carcinoma

Background: The prediction of biologic behavior of poorly cohesive early gastric carcinoma (EGC) is an important issue in the selection of the treatment modality. To elucidate the risk factors for lymph node metastasis (LNM) of poorly cohesive EGC, we focused on the histologic purity of the poorly cohesive component and evaluated the impact of this factor on LNM. Methods: We divided poorly cohesive EGC into (1) pure signet ring cell (SRC) carcinoma, which was defined as composed only of signet ring cells or poorly cohesive cells and (2) mixed SRC carcinoma, defined as poorly cohesive carcinoma with minor tubular components. We reviewed the clinicopathologic features, including age, sex, location, size, depth, lymphovascular invasion (LVI), LNM, ulceration, and intestinal metaplasia between the two groups in a large series of poorly cohesive, submucosa-invasive EGC (n = 317). Results: LNM was found in 58 cases (18.3 %). Mixed SRC carcinoma histologic type (p < 0.001), larger tumor size (more than 2 cm) (p = 0.012), and the presence of LVI (p < 0.001) were associated with LNM. Pure SRC carcinomas accounted for 56.2 % (178/317) of the cases. Fourteen pure SRC carcinomas (7.8 %) showed LNM, whereas 44 mixed SRC carcinomas (31.9 %) exhibited LNM (p < 0.001). On multivariate logistic regression, the presence of LVI (odds ratio 6.737; 95 % confidence interval 2.714–16.720; p < 0.001) and mixed SRC carcinoma histologic type (odds ratio 4.674; 95 % confidence interval 2.370–9.216; p < 0.001) were independent predictors of LNM in poorly cohesive, submucosa-invasive EGC. Conclusions: The presence of a tubular component in SRC carcinoma was a risk factor for LNM in poorly cohesive, submucosa-invasive EGC. On the basis of this finding, we propose that the presence of a minor tubular component or the purity of the poorly cohesive/SRC carcinoma component should be reported in daily pathologic practice.