Mediastinal Cyst Disclosed by a Single Episode of Dyspnea

Case Presentation:

We present a twenty‐one year old AA female with a past history significant only for premature birth, referred by her physician for evaluation of a single brief episode of dyspnea at rest and an abnormal CXR. ROS disclosed a history of intermittent palpitations. On examination, vital signs were unremarkable. Lung examination revealed rightward tracheal deviation, decreased breath sounds, dullness to percussion and decreased tactile fremitus on the left hemithorax. Cardiac exam disclosed JVD, PMI palpated in right 2nd ICS with heart sounds best heard at the right parasternal border. CXR revealed a left hemithorax opacification with left lung compression and a right shift of mediastinal structures. A CT scan confirmed an anterior mediastinal mass with minimal calcification within its wall, extending into the left hemithorax, totally compressing the left lung. There was no obvious invasion of the mediastinal structures. PFTs revealed a moderate‐severe restrictive defect with no diffusion abnormality. ABG confirmed normal oxygenation and ventilation. 12‐lead EKG was significant for low precordial lead amplitude. Lab workup including CBC, CMP and thyroid function was in normal limits. AFP and bHCG were negative. Initial impression was that of a mediastinal cyst versus thymoma versus teratoma. She was admitted and prior to surgery underwent CT guided drainage of the cyst removing about 1200ml of fluid which was negative for malignancy or infection. She then underwent a mediastinotomy with excision of a large cyst which had no obvious attachment to mediastinal structures. The cyst was grossly 24×10×8 cm with a fibrous capsule. Microscopically the cyst showed epithelial lining of both squamous and columnar types. There was no cartilage, thymic or malignant histology noted. Post surgical course was uneventful and the patient was discharged with a CXR revealing almost a complete re‐expansion of the left lung.

Discussion:

Cysts of the mediastinum, are generally benign and mostlycongenital in origin. They represent 12‐30% of all primary mediastinal tumors. Classification is based on their histologic pattern with grouping into foregut derived (brochogenic, esophageal), mesothelial (pericardial, pleural), thymic, neuroenteric, thoracic duct, and miscellaneous cysts.

Conclusion:

Due to the lack of histologic features consistent with any of the afore mentioned types, it was concluded that this patient had cyst of the miscellaneous variety. Mediastinal cysts are commonly asymptomatic, and are usually incidentally diagnosed on routine radiographs. Clinicians should think of this possibility in the presence of opacity in the chest as these cysts have a tendency to rupture leading to sudden death. These cysts have a low rate of recurrences; surgery can be done with a low morbidity and mortality and offers a definitive cure.

Author Disclosure Block:

V. Melinamani, None; L. Lovett, None.