Introduction: The most common benign lesion of the diaphragm is a cyst, most often either a mesothelial cyst or a bronchogenic cyst. Mesothelial cysts are congenital lesions arising from coelomic remnants, which can be found in the adrenal gland, ovary, falciform ligament, spleen, vaginalprocess of the testicle, mesentery, and, rarely, the diaphragm. Presentation of cyst in adults was even more uncommon than in children and was most often symptomatic, with patients complaining of chest pain, upper abdominal discomfort, and dyspnea.
Case Presentation: A 74-year-old woman presented with chest pain and shortness of breath. Cystic lesion was detected in patient examinations between the diaphragm leaves. The patient was operated and a cystic lesion of 5×7 cm was found filling the cardiovphrenic sinus. When the cyst membrane was opened, it was directly related to the peritoneum. Primary repair of the defect was performed using the cyst membrane. The patient was discharged on the 5th postoperative day. Pathologic examination revealed muscle fibers in the cyst membrane.
Conclusion: Asymptomatic cysts could be managed conservatively and symptomatic cysts approached surgically or percutaneously. In the differential diagnosis, hydatid cyst should be kept in mind.