Lymphovascular invasion and lymph node metastasis rates in papillary adenocarcinoma of the stomach: implications for endoscopic resection

Background: Current Japanese gastric cancer treatment guidelines recommend the same endoscopic resection criteria for papillary early gastric cancer (EGC) and well-differentiated (WD) or moderately differentiated (MD) EGC. To evaluate the appropriateness of this recommendation, we compared the clinicopathological characteristics of papillary EGC with those of WD, MD, poorly differentiated (PD), and signet ring cell (SRC) EGC. Methods: A total of 6710 patients who underwent radical gastrectomy for EGC were included. Clinicopathological characteristics of papillary EGC were retrospectively reviewed and compared with those in other EGC subtypes. Results: Papillary EGC accounted for 1.9% (130/6710) of total cases. Patients with papillary EGC were older and showed a male predominance compared to patients with PD or SRC EGC. Papillary EGCs showed significantly higher submucosal and lymphovascular invasion rates than WD or MD EGC or PD or SRC EGC. However, the LN metastasis rate of papillary EGC was comparable to or lower than that in other EGC subtypes. LN metastasis rates in mucosal cancers were 1.5%, 1.1%, and 4.0%, and those in submucosal cancers were 9.4%, 11.9%, and 17.6% for papillary EGC, WD or MD EGC, and PD or SRC EGC, respectively. In multivariate analysis, lymphatic invasion and PD or SRC histology were the strongest risk factors for LN metastasis. Among 63 papillary EGC that met the curative endoscopic resection criteria, no case showed LN metastasis. Conclusions: Endoscopic resection can be indicated for papillary EGC according to current guidelines. Given a considerable lymphovascular invasion rate, careful histological evaluation is required after endoscopic resection for papillary EGC.