Background: CD24, a mucin like cell surface adhesion molecule and a ligand for P-selectin, has been reported as a prognostic factor in a variety of human cancers. However, the role of CD24 in gastric adenocarcinoma remains largely unknown. Methods: The expression pattern of CD24 in 103 gastric adenocarcinomas (31 diffuse type, 60 intestinal type , and 12 mixed type) was analyzed by immunohistochemistry. Results: Cytoplasmic CD24 expression occurred in 50% of the gastric adenocarcinoma patients and was associated with high -stage tumor (Stage III-IV, P = .023 ), serosal invasion (SI, P = .010), lymphovascular invasion (LVI, P = .039 ), and lower 10-year survival (P = .0238). The CD24 staining pattern was different in intestinal and diffuse-type gastric adenocarcinomas. However, the tumor thrombi in lymphovascular spaces exhibited strong cytoplasmic CD24 expression in both types. Further analysis showed that cytoplasmic CD 24 expression was, in fact, correlated with high-stage tumor, SI, LVI, and lower 10-year survival significantly (P = .020, P = .007, P = .018, P = . 0285, respectively) in diffuse-type gastric adenocarcinoma. Moreover, multivariate analysis showed that cytoplasmic CD24 expression was an independent risk factor of SI and LVI respectively (P = .0083 and P = . 0019), and thus it contributed to high-stage tumor and poor patient survival in diffuse- or mixed-type gastric adenocarcinoma. Conclusions: Cytoplasmic expression of CD24 was associated with invasiveness and poorer prognosis and can serve as a novel target for prognostic prediction and adjuvant treatment of patients with diffuse-type gastric adenocarcinoma after tumor resection. ; 病理學科暨研究所 ; 醫學院 ; 期刊論文