Retroperitoneal Malignant Peripheral Nerve Sheath Tumour: A Rare Case Report

Abstract

A 21-year-old female patient with left hip pain, ongoing for 5-6 months and painful swelling in the left buttock, was admitted to hospital. No other symptoms, including muscle atrophy, weakness and functional limitation were noted. On examination, a partially mobile subcutaneous mass was observed in the left hip. An informed consent was taken for the surgical procedure and the patient was operated immediately. The mass was removed in toto, under local anaesthesia. On macroscopic examination, a 2x1,5x1,5cm nonencapsulated mass was noted. On microscopic examination, a non-encapsulated lesion from the reticular dermis extending into the subcutaneous fat tissue was observed. Enlarged nerve branches formed tortuous masses within delicate musinous stroma in the lesion. These nerve branches involved long cells with wavy dark nucleus. The cells were intertwined. In these cells, changes such as nuclear atypia and an increased number of mitotic activity that may be associated with malignancy, were not observed.On the immunohistochemical examination, the cells within the nerve fascicles were positive for S100. Based on these findings, the lesion was diagnosed as Plexiform Neurofibroma. Plexiform Neurofibromas are common lesions in NF1. For this reason, the patient was recalled for a complete clinical examination. It was noted that the patient's father had NF1. On physical examination, two cafe-au-lait macules on the forearm, approx 20mm in diameter, were noted. Lisch nodules in both eyes were noted. National Institute of Health diagnostic criteria for NF1 (1997) was used and the patient was diagnosed with NF1. It was noted that the patient had been suffering from left-hip pain even after excision of the subcutaneous mass. Thus an MRI of the lumbar and lower abdomen revealed a second mass in the left half of the pelvis-in the left-midline pushing the left ovary to the inferior.In lumbar spinal MRI, heterogeneous presacral mass was seen in the sagittal sections. In pelvic MRI, presacral partially enhancing mass was seen respectively in transverse, sagittal and coronal sections. The mass extend till S2 neural foramen [Table/ Fig-1a-d].A surgery was planned and it was found that the mass originated in sacral roots. The mass was totally excised. It measured 6x5x4.5cm, ABSTRACTMalignant nerve sheath tumours (MPNST) are rare neoplasias and retroperitoneal cases are fairly rare and clinically difficult to be detected, but they are very agressive neoplasias. MPNST are frequently seen in head, neck and upper extremities. In patients with NF1; MPNST, a poor-prognostic lesion, may result from a malignant degeneration of a former plexiform neurofibroma. It is necessary to be aware of a potential malignancy in patients diagnosed with plexiform neurofibroma.We present a 21-year-old female with a diagnosis of MPNST. The patient was admited to the hospital because of a tumour in the subcutaneous region on her left buttock. The surgeon's clinical diagnosis was lipoma. After the pathological examination of biopsy specimen, the lesion was id...

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