1Department of Radiology, Kagawa Rosai Hospital, 2Department of Urology, Kagawa Rosai Hospital, 3Department of Surgery, Kagawa Rosai Hospital, 4Department of Pathology, Kagawa Rosai Hospital, 5Department of Surgery Eisei Hospital
Although retroperitoneal schwannoma is an uncommon retroperitoneal tumor, it is not rare: more than two hundred cases have been reported in Japan. Most of these tumors were large, about 10 cm in diameter. Characteristic sonogarphic findings include large size, sharply demarcated contour, low echoic mass, and internal cystic degeneration. Here we present two cases of small retroperitoneal schwannomas that measured 28×24×26 mm and 30×30×39 mm. One, a round mass behind the pancreatic body, produced a solid pattern, internal high echo spots, and slight cystic change. The other, a round anechoic mass near the left adrenal gland, had posterior echo enhancement similar to that of a cysy; however, the presence of enhancement on contrast-enhanced CT showed that it was not a cyst. Both tumors were surgically removed, and the pathologic findings were reviewed. The first tumor was a so-called ancient schwannoma, a schwannoma that had undergone marked degenerative changes: it appeared cystic and hemorrhagic, and calcification was also present. The other was a homogeneous tumor containing mostly Antoni types A and B. A small retroperitoneal schwannoma would not appear as a homogeneous mass without cystic degeneration; it would show signs of cystic degeneration like those typical of large retroperitoneal schwannoms.