MR imaging features of giant pre-sacral schwannomas: a report of four cases.

Benign giant sacral schwannoma is an uncommon cause of destruction of the sacrum. This report details four cases of a variant of this condition called giant presacral schwannoma (GPSS). On MR imaging the features are of a large, well-defined presacral soft tissue mass, arising just to one side of the midline with minor involvement of the bone. The typical MR features of a benign peripheral nerve sheath tumour are not seen. The tumours appear heterogeneous due to long-standing degeneration. Biopsy is advocated as the appearances of GPSS can be similar to a malignant peripheral nerve sheath tumour (malignant schwannoma).