Retropleural teratoma presenting as an abdominal mass in a 9-month-old boy

Teratomas are rare tumors that present most commonly in the anterior mediastinum and retroperitoneum. To date, the retropleural primary site has not been reported.

A 9-month-old boy presented with a large, painless, right-sided abdominal mass. Laboratory values, including tumor markers α-fetoprotein and β-human chorionic gonadotropin, were within normal limits. Diagnostic imaging, including abdominal ultrasound, computed tomographic scan, and magnetic resonance imaging, suggested a large retroperitoneal mass consistent with a teratoma. Because the mass was thought to be arising from the retroperitoneum, an abdominal approach was chosen. After adequate exposure, it became clear that the tumor was arising from above the diaphragm. The diaphragm was incised, and the pleural cavity was entered. The tumor was found in the retropleural space where it was dissected away from the inferior vena cava, aorta, and chest wall. The patient recovered without complications.

Histologic examination revealed a mature cystic teratoma with no malignant features. The patient has been disease-free at 7-year follow-up, based upon both clinical examination and diagnostic imaging.

This is the first case report of a teratoma arising from the retropleural space. Preoperative imaging may be inaccurate for guiding surgical planning because the diaphragm may not be clearly visualized with current diagnostic techniques. Surgeons should be cautious regarding the location of tumors that arise near the diaphragm and should plan surgical resection carefully.