Endoscopic resection is curative for superficial esophageal squamous cell carcinoma (ESCC) limited to the lamina propria. Endoscopic resection is not recommended for superficial ESCC invading muscularis mucosa or submucosa, however, because of the high frequency of lymph node metastasis (LNM) in such patients. Methods to more accurately predict LNM by analysis of endoscopically resected specimens are needed. Patients with superficial ESCC who underwent surgery without prior chemoradiotherapy (n= 110) were retrospectively examined to determine whether LNM correlated with immunohistochemical parameters and conventional histological parameters, including depth of invasion and vascular permeation. Cancer cell expression of claudins-1, 5, and 7, E-cadherin, beta-catenin, and matrix metalloproteinase 7 was evaluated. Univariate analysis revealed that LNM correlated with claudin-5 expression, but not any other immunohistochemical parameter examined. Multivariate analysis revealed three independent risk factors for LNM: aberrant claudin-5 expression in cancer cells (odds ratio; OR [95% confidence interval]= 4.61[1.44-14.77]), depth of submucosal invasion greater than 200 microm (3.55 [1.02-13.17]), and positive lymphatic permeation (3.34 [1.22-9.15]). LNM was found in one of 29 (3.4%) patients with none of these three risk factors, and in 32 of 81 (39.5%) patients with one or more of these risk factors. In superficial ESCC, routine analysis of claudin-5 expression in cancer cells together with depth of invasion and lymphatic permeation may be useful for predicting LNM and thereby reducing the number of patients undergoing additional surgery after successful endoscopic resection.