A case of a schwannoma of the greater omentum

Abstract

We report a case of a schwannoma of the greater omentum.
A 59-year-old woman was admitted to the hospital because of epigastric distress. An abdominal CT scan showed a well-defined cystic tumor 10cm in diameter with calcification located in the right upper abdominal cavity. This tumor was filled with liquid component containing low signal on T1-weighted and high signal on T2-weighted images in MRI. An operation was carried out, though no definite diagnosis was made. Upon laparotomy, the tumor was found to continue to the greater omentum partly and to be fed by a vessel branching from the right gastroomental artery. The tumor with part of the greater omentum was removed. The removed tumor was a multilocular tumor containing an orange transparent serous component with a part of solid tissue. Histopathologically the tumor was composed of numerous spindle-shaped cells with round nuclei which were positive for S-100 protein and negative for KIT. It was thus diagnosed as Antoni B type benign schwannoma.
Schwannoma of the greater omentum is so extremely rare that only 8 cases have been reported in Japan. It is difficult to diagnose this disease preoperatively for lack of subjective symptoms and specific imaging findings. We should consider a schwannoma as a probable differential diagnosis of the tumor in the greater omentum.