BACKGROUND : The tumor, node, metastasis classification system for staging esophageal cancer does not include tumor volume although it may be an important prognostic factor. We evaluated the prognostic value of tumor volume in esophageal cancer. METHODS : We performed a retrospective study in patients with histologically confirmed primary esophageal cancer who underwent curative esophagectomy at our facility between April 1992 and December 2013. The Tumor Depth Parameter (TDP) was defined as mucosa = 1, submucosa = 2, muscularis propria = 3, adventitia = 4, and invasion into adjacent organs = 5. The pathological Tumor Volume Index (TVI) was defined as the major axis × the minor axis × TDP. The appropriate tumor diameter and TVI cutoff values were determined by the Youden index obtained from the receiver operating characteristic curve. Prognostic factors for overall survival were evaluated by univariate analysis and Cox proportional hazards regression models. RESULTS : We enrolled 302 patients. In the univariate analysis, patient age and sex, thoracoscopic surgery, tumor depth of invasion and diameter, lymph node metastasis, and the TVI were significantly associated with overall survival. In our multivariate analysis, patient age and sex, thoracoscopic surgery, lymph node metastasis, and the TVI were independently associated with overall survival. CONCLUSIONS : The pathological TVI was an independent prognostic factor in patients with esophageal carcinoma and could be included in the staging system of esophageal cancer.