This paper reports a surgically treated case of undifferentiated carcinoma with lymphoid infiltration of the esophagus. Histologically, most of the tumor consisted of undifferentiated carcinoma (non-small cell type) with lymphoid infiltration and a small portion showed features of poorly differentiated squamous cell carcinoma. Carcinoma with lymphoid infiltration in the stomach, breast or nasopharynx has a good prognosis, but in the esophagus this histological type is extremely rare and its characterization is unclear. This is only the sixth report to date of undifferentiated carcinoma with lymphoid infiltration of the esophagus.