Retropleural teratoma presenting as an abdominal mass in a 9-month-old boy Kenneth W. Gow a, ⁎ , Curt S. Koontz a , Paula Dickson b , Lee Bannister c , Bahig Shehata c a Division of Pediatric Surgery, Department of Surgery, Emory School of Medicine, Atlanta, GA 30322, USA b Department of Radiology, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA c Department of Pathology, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA Received 9 June 2010; revised 7 July 2010; accepted 9 July 2010 Key words: Teratoma; Retropleural; Thoracic Abstract Background: Teratomas are rare tumors that present most commonly in the anterior mediastinum and retroperitoneum. To date, the retropleural primary site has not been reported. Case Presentation: 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. Results: 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. Conclusion: 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. © 2010 Elsevier Inc. All rights reserved. Teratomas are germ cell tumors that arise in children from a variety of locations. They are believed to originate from primordial cells with the potential to differentiate into many different types of tissue. They most commonly arise from the sacrococcygeum, ovary, testis, and mediastinum. We describe the first case of a teratoma arising from the retropleural location and discuss some of the potential difficulties in diagnosis and surgical resection that arose. Furthermore, this site of origin raises questions as to the exact nature by which teratomas arise. ⁎ Corresponding author. W-7729, Seattle, WA 98105, USA. Tel.: +1 206 987 2794; fax: +1 206 987 3925. E-mail address: kenneth.gow@seattlechildrens.org (K.W. Gow). www.elsevier.com/locate/jpedsurg 0022-3468/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2010.07.014 Journal of Pediatric Surgery (2010) 45, E15–E18