Circumferential Resection of an Extracardiac Mediastinal Teratoma

Patient Details

A fifteen-year-old boy with a past medical history of asthma presented with sudden onset chest pain and orthopnea. Imaging workup in the emergency department included a chest X-ray that suggested a mediastinal mass. (A cardiac CT was initially deferred given the patient’s clinical stability.) Advanced cardiac imaging with MRI was chosen for superior soft tissue characterization and avoidance of ionizing radiation. The MRI demonstrated a right-sided mass in the anterior mediastinum measuring 8.3 by 4.2 by 4.3 cm. The mass was intrapericardial with no direct atrial involvement. There was slight compression of the right atrium and minimal shifting of the superior vena cava. The mass was composed of a solid exterior and cystic interior. Because of its position relative to the right atrium and right lung, the patient was scheduled for removal via a median sternotomy.

Operative Procedure

A midline sternotomy was performed, and the pericardium was divided from the innominate vein to the diaphragmatic surface with electrocautery. Caseous material from the mass was present within the pericardium. Next, the right pleural space was opened to begin dissection of the mass along each margin. Throughout the dissection, the right phrenic nerve was in close association with the mass along its anatomic course to the diaphragm. Prior to complete removal, the cystic components began to drain from the mass. After total excision, surgical clips were placed to delineate the tumor margins. The remnant of the thymic tissue was removed in its entirety. Because of the caseous material found within the mediastinum, the chest was irrigated and suctioned with two liters of sterile saline followed by one liter of sterile water. The patient was extubated in the operating room and transferred to the cardiovascular intensive care unit for further care.

Pathologic and Microbiologic Report

Histologic and gross examination identified the mass as a mature cystic teratoma consisting of benign thymic tissue with focal cystic change. The interior of the mass showed a unilocular cystic cavity containing amber brown, grumous debris and hair. Immunohistochemical staining of the mass was negative for malignancy. Aerobic and anaerobic cultures were negative. A Gram stain showed no organisms, and no fungal elements were noted.

Postoperative Course

A postoperative chest X-ray revealed a normal functioning right hemidiaphragm and adjacent surgical clips around tumor margins. The patient received appropriate antibiotic prophylaxis with vancomycin, cefepime, and metronidazole. His postoperative course was uneventful, and he was discharged three days after surgery. A follow-up two weeks after surgery demonstrated respiratory improvement and complete resolution of symptoms.

References

1. Tian Z, Liu H, Li S, et al. Surgical treatment of benign mediastinal teratoma: summary of experience of 108 cases. J Cardiothorac Surg. 2020;15(1):36.
2. Chang CC, Chang YL, Lee JM, et al. 18 years surgical experience with mediastinal mature teratoma. J Formos Med Assoc. 2010;109(4):287-292.
3. Yendamuri S. Resection of a Giant Mediastinal Teratoma. Ann Thorac Surg. 2016;102(5):e401-e402.

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