Cyst with Mullerian differentiation in the anterior mediastinum and compression of the brachiocephalic vein reluting in consecutive thrombosis

Background:

42 year old female patient presented with tenderness in the left neck refractory to pain medication. Later she noticed swelling of the left arm which led to further diagnostic via CT-scan with diagnosis of a 4.7 × 3.5 cm cystic formation in the anterior mediastinum. The tumor compressed the brachiocephalic vein resulting in thrombosis of both left jugular and subclavian vein. Therapy with NOAC was established.B-symptoms were denied and excision of the cystic formation was scheduled.

Material and method:

Standard approach for a right sided thoracoscopic thymectomy with three ports. After incision of the mediastinal pleura along the phrenic nerve the cystic formation was identified and protruded in the pleural cavity, but seemed to be partially solid. Therefore we avoided to puncture the cyst to reduce size in order to generate more space. A partial sternotomy was performed and complete resection of the thymus with the tumor achieved while the brachiocephalic vein was preserved. The specimen was sent to pathology for histological analysis.

Result:

Histological analysis showed an unilocular cyst (maximal diameter 5 cm) with clear fluid, and normal thymic tissue without malignancy. The cyst showed epithelial cells, tested positive for PAX8 and estrogen receptors compatible with the diagnosis of a Mullerian derived cyst of the mediastinum. After resection and anticoagulation for further 3 months the CT-scan showed complete resolving of the thrombosis with patency of the veins.

Conclusion:

According to literature this is the first case of a mediastinal cyst with Mullerian differentiation in the anterior mediastinum and compression of the brachiocephalic vein reluting in consecutive thrombosis. While thymic cysts are a rather common cause for cystic formations in the anterior mediastinum a Mullerian derived cysts, first described by Hattori in 2005, are rare and usually located in the posterior mediastinum. The etiology of Mullerian derived cysts in the mediastinum is unclear and there are only 19 cases reported, all of them located in the posterior mediastinum. The clinical behavior of these cysts appears to be benign and comparable outcome as other mediastinal cysts. Complete resection due to a vascular complication was mandatory in this case and resulted in a complete recovery of the thrombosis.