Histological mixed-type as an independent risk factor for nodal metastasis in submucosal gastric cancer

Recent studies reported that the histological mixed-type, which consists of differentiated and undifferentiated components, was related to the aggressive clinical features of gastric cancer as well as its poor outcomes. This study was designed to investigate the influences of the mixed-type on lymph node metastasis in patients with submucosal gastric cancer. We analyzed a total of 239 consecutive patients who underwent curative gastrectomy for submucosal gastric cancer between 2004 and 2012 from their hospital records. The overall prevalence of histological mixed-type in submucosal gastric cancer was 46.9 % (112/239). The histological mixed-type correlated more strongly with lymph node metastasis (P = 0.0016; 25.0 % (28/112)) than the undifferentiated type in the Japanese classification of gastric carcinoma (JCGC) (P = 0.2779; 20.5 % (17/83)) and 7th tumor-node-metastasis (TNM) (P = 0.0476; 20.7 % (31/150)) classifications. Univariate and multivariate logistic regression analyses identified a tumor size of 25 mm or greater (P = 0.0003, OR 4.51 (95 % CI 1.95-11.9)) and the histological mixed-type (P = 0.0316, OR 4.02 (95 % CI 1.12-19.2)) as independent risk factors for lymph node metastasis. The incidence of lymph node metastasis was high in patients with both these factors (33.8 % (23/68)) and low in patients without both factors (3.0 % (2/67)). These results suggest that the histological mixed-type correlated more strongly with lymph node metastasis than the undifferentiated type in the JCGC and TNM classifications and highlight its usefulness as a risk factor for lymph node metastasis in submucosal gastric cancer.