Abstract
A 63-year-old woman complained of an abdominal tumor. Abdominal computed tomography (CT) showed a retroperitoneal tumor, 13 cm in diameter, with heterogeneous density. Magnetic resonance imaging (MRI) showed that the tumor consisted of both cystic and solid density areas, and the surface was smooth. Evaluation by 18 fluro-2-deoxy glucose positron emission tomography (FDG-PET) showed a high accumulation (SUV max 8.5) of FDG in the PET, and the standard uptake value (SUV) max in the delayed phase was 9.5. Based on a diagnosis of mesenchymal tumor of the retroperitoneum, we removed the tumor during laparotomy. We observed that the tumor had a smooth surface and was located in the retroperitoneal space around the aortic bifurcation as expected from the CT images, and did not directly invade the small intestine or colon. The tumor diameter was 12.5 × 10.5 × 8.5 cm. The cut surface of the tumor was yellowish and included a cystic formation. Microscopically, the spindle tumor cells infiltrated with a wavy pattern, and virtually no mitosis. In immunohistochemistry, the tumor cells were positive for S100, but negative for KIT, CD34, and α-SMA. Therefore, this tumor was diagnosed as retroperitoneal schwannoma. We reported a retroperitoneal schwannoma with a high accumulation in PET, and reviewed the FDG-PET findings from nine cases of retroperitoneal schwannomas already reported in Japan.
