Generally, benign lesions, which make up the majority of mediastinal tumors and cysts, are asymptomatic; however, they may produce clinical findings. We report on a patient with presumed silent esophageal perforation whose clinical and radiologic assessment was suggestive of massive paraesophageal hiatus hernia. However, surgery revealed a paraesophageal cyst and histology was reported as acute organizing pleurisy. A reasonable, tentative, preoperative diagnosis for each mediastinal lesion can be frequently made by considering its location in the mediastinum, the age of the patient, the presence or absence of local or constitutional symptoms and signs, and the association of a specific systemic disease state. However, the precise nature of a lesion in the mediastinum, as elsewhere, cannot be determined without histologic examination of the tissue. To our knowledge, this unusual clinical case is not been reported in the literature.