Retroperitoneal giant schwannomas: report on two cases and review of the literature.

The occurrence of massive retroperitoneal schwannomas is extremely rare and their presence may only be expressed by insidious onset of non-specific and misleading symptoms with a predominance of lower back pain. MRI scan as the imaging procedure of choice will demonstrate the tumour location and its relation to the surrounding structures, but due to heterogeneity and degeneration in some tumours, it may mimic malignancy. Hence tissue sampling through needle biopsies are essential to verify the diagnosis prior to surgery. Tumour excision in toto is considered the treatment of choice, but it can be hazardous especially if the tumour is adherent to the presacral venous plexus. Severe bleeding complications due to the damage of venous structures have to be encountered, and establishing lasting haemostasis may pose considerable difficulties. Hence surgery should be attempted with full precautions, and preoperative counseling of the patient. If malignancy can safely be excluded, laparoscopic piecemeal excision should be considered as an alternative treatment as recurrence is unlikely. Definition of the originating nerve might not always be possible and a minor degree of neurological impairment has therefore to be anticipated.