[Retroperitoneal schwannoma: a report of two cases and review of the literature].

Two cases of retroperitoneal schwannoma, one malignant, and the other benign, are herein reported. The first case was a 71-year-old female with a complaint of dull right flank pain. CT scan showed a large mass, which occupied almost the whole right half of the abdominal cavity extraperitoneally, accompanied by a low density portion in its central part. Angiography showed several feeding arteries, such as intercostal arteries, lumber arteries, and so on. Many tortuous and thin irregular vessels were seen. Tumor excision was performed under the diagnosis of malignant retroperitoneal tumor. No surrounding invasion or metastasis were seen. The tumor had a thick capsule, and cut surface showed lobulated appearance. No adjuvant therapy was done. Histological diagnosis was low grade malignant schwannoma. She is alive and well 17 months postoperatively. The second case was a 64 year-old male. His tumor was found incidentally, when he underwent a close examination of his gastric ulcer. According to CT scan, it was located behind the left kidney, and had a diameter of 3.0 X 2.5 cm. The tumor was removed including the fascia of lateral edge of quadratus lumbolum muscle, where it was firmly attached to. Surgical specimen showed a doughnut like appearance, because of its marked central necrosis. It had a white and thick capsule. Histological diagnosis was benign schwannoma of two different types, Antoni A and B. He remains well 13 months after operation. The 113 benign cases and 55 malignant cases reported in Japan, including our cases, were reviewed and discussed.