Tumor size predicts survival in mucinous gastric carcinoma

Background Mucinous gastric carcinoma (MGC) is a distinct histologic subtype of gastric cancer. However, the prognostic significances of the current TNM staging system and histology in MGC have not been studied. Methods 206 patients who underwent R0 resection for MGC were classified by tumor size (<3 cm as T1; ≥3-5 cm as T2; ≥5-9 cm as T3; and ≥9 cm as T4). Immunohistochemistry for EGFR and HER2 was also performed. Results Tumor sizes ranged from 1.2 to 21.0 cm (median 6.2 cm). Large tumor size (≥5 cm) was significantly associated with older patient age, deeper invasion depth, and more frequent lymph node metastasis (P < 0.05). Tumor size was a significant prognostic factor in both univariate (P < 0.001) and multivariate (P < 0.04) analyses. However, depth of invasion was not significant in multivariate analyses. A modified staging system based on tumor size predicted survival more accurately than did the conventional TNM staging system. We verified our results in an independent validation cohort of 123 MGC patients. Overexpression of either EGFR or HER2 was rare. Conclusions In MGCs, tumor size is an independent prognostic factor and a modified TNM system based on tumor size predicted survival accurately.