Benign retroperitoneal neurilemmoma--a case report.

Retroperitoneal neurilemmomas are the rarest of all retroperitoneal tumours. A rare case of a very large benign retroperitoneal neurilemmoma is presented. Pre-operative diagnosis of these tumours is difficult and the majority are asymptomatic. They are usually detected as an abdominal mass on routine examination as in this case. Despite severe displacement and distortion of the inferior vena cava in this patient, there were no clinical abnormalities detected. The predominantly cystic nature of the tumour was well demonstrated by ultrasound and CT scan examination but the true nature of the tumour could not be diagnosed. It is very rare for these tumours to be malignant and recurrence after surgical excision is rare.