The middle mediastinum contains several important organs and pluripotent cells. It is difficult to make a definitive diagnosis in patients with middle mediastinal tumors due to a wide range of diseases. The likelihood of malignancy is influenced primarily by the following factors: patient age, size, tumor location, and the presence or absence of symptoms. We describe a case of a middle mediastinal tumor, which was suspected on chest x-ray; chest computed tomography revealed the eccentric mass of distal esophagus. This case emphasizes the diagnostic importance of the chest x-ray to the physicians. The possible differential diagnoses are reviewed.