Retroperitoneal Malignant Peripheral Nerve Sheath Tumor in the Pelvic Cavity without Neurofibromatosis I

Abstract

We present a rare case of malignant peripheral nerve sheath tumor (MPNST) in the pelvic cavity. A 58-year-old woman presented with pain in her buttocks and left leg. She had no signs of neurofibromatosis I. CT and MRI showed a tumor 10 cm in diameter in the pelvic cavity. Since it was very hyperintense on T2-weighted MR imaging, we suspected a neurogenic tumor. Tumor resection, including the capsule, was performed. Histologically, multinuclear tumor cells were seen, and we made a diagnosis of MPNST arising from the pelvic plexus. There are no signs of recurrence 6 years and 3 months after the operation. It is said that about 50% of MPNST are associated with von Recklinghausen neurofibromatosis (NF I). In this case, we could not find any signs of NF I. Furthermore, MPNST are most often located in the limb and the body trunk. We thought that this is a rare case of MPNST originating in the pelvic plexus.