Benign giant schwannoma located in the upper arm.

A 72-year-old-female presented with a giant schwannoma on the medial side of her right upper arm. Ultrasonographic and magnetic resonance imaging examinations showed that it was almost a totally cystic lesion. It was initially misdiagnosed as a hydatid cyst. After excision of the tumor, histopathological examination revealed that it was a schwannoma composed of two types of regions known as Antoni A and B regions. The tumor was 15 x 8 x 7 cm in size. There were no neurological sequelae after the operation. This is probably the biggest schwannoma of the upper extremity reported.