Staging of gastric cancer: Comparison of post-operative pathologic staging to pre-operative CT and endoscopic ultrasonographic staging.

11 Background: Stomach CT and endoscopic ultrasonography are used for evaluating pre-operative staging of gastric cancer. The aim of this study was to compare the pre-operative CT and endoscopic ultrasonographic staging to post-operative pathologic staging. Methods: We reviewed medical records of 567 patients with gastric cancer from 2012 to 2015, and compared their pre-operative CT staging to post-operative pathologic staging. Among the 567 patients, 149 patients underwent pre-operative endoscopic ultrasonographic staging, so we compared their pre-operative endoscopic ultrasonographic staging to post-operative pathologic staging. We also investigated lymph node metastasis in 146 patients with gastric cancer invading submucosa, planning to undergo endoscopic submucosal dissection. Results: The numbers of patients diagnosed as T1, T2, T3, T41, and T4b by pre-operative CT staging were 327, 97, 93, 46, and 4, respectively. However, the numbers of patients diagnosed as T1, T2, T3, T41, and T4b by post-operative pathologic staging were 208, 153, 53, 83, 62, and 8, resulting the pre-operative CT staging to be under-estimated. Similarly, pre-operative endoscopic ultrasonographic staging was also under-estimated, as although 48, 67, 32, and 2 patients were diagnosed as T1a, T1b, T2, and T3, respectively, by the pre-operative endoscopic ultrasonographic staging, post-operative pathologic staging revealed 72, 55, 13, 7, and 2 patients. In patients with gastric cancer invading submucosa (sm), there were 56 patients with sm1 invasion, 32 patients with sm2 invasion, and 91 patients with sm3 invasion. Lymph node metastasis was observed in 7 patients with sm1 invasion, 3 patients with sm2 invasion, and 22 patients with sm3 invasion. Poorly cohesive gastric cancer was the most common pathologic diagnosis in patients with metastatic lymph node. Conclusions: Physicians should keep in mind that pre-operative stomach CT and endoscopic ultrasonographic staging can be under-estimated compared to post-operative pathologic staging. Also, patients with poorly cohesive adenocarcinoma had more lymph node metastasis than patients with differentiated adenocarcinoma.