: Regulatory T cells (Tregs) are known to be key regulators of immune responses in patients with autoimmune disease and infection and also for attenuating antitumor immunity by the host. It has been reported that high numbers of tumor-infiltrating Tregs might be associated with poor clinical outcomes for several malignant tumors. Therefore, this study aimed to examine the impact of tumor-infiltrating Tregs on the prognosis of gastric carcinoma patients. Methods : The immunohistochemical

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... for anti-fork head Box P3 (FoxP3) antibody was performed by using a 3 mm core from the tumor specimens of each of the 173 gastric cancer patients for constructing a tissue microarray. FoxP3-positive Tregs were quantified by calculating the numbers of positive cells per 5 high-power fields on light microscopy. Thereafter, the 173 patients were subdivided into the low Tregs group (≤ 3/5 high power fields [HPF], n = 41) and the high Tregs group (> 3/5 HPF, n = 132). Results : The high Tregs group was significantly associated with a higher stage, more invasion depth and lymph node metastasis (p = 0.009, p = 0.036, p = 0.006, respectively). The high Tregs group showed significantly poorer overall survival and event-free survival (p = 0.004, p = 0.017, respectively) on the univariate analysis. The Tregs group and the tumor, node and metastasis stage were also independent prognostic factors that were significantly associated with overall survival (p = 0.025, p < 0.001, respectively) by multivariate analysis. Conclusions : Our results indicated that a high number of tumor-infiltrating FoxP3-positive Tregs could be an indicator of poor long term survival for gastric carcinoma patients.