When the nerves turn malignant: A case of retroperitoneal peripheral nerve sheath tumor: A case report

Abstract

Introduction: Retroperitoneal malignant peripheral nerve sheath tumors (MPNST) are uncommon soft tissue sarcomas, usually presenting late because of the wide potential space. Preoperative diagnosis is difficult, and treatment mainly consists of surgical resection. Case Presentation: A 59-year-old man presented with abdominal pain for one month. Contrast-enhanced CT abdomen disclosed a huge heterogeneously enhancing retroperitoneal mass (11.9 × 11.1 × 15.7 cm) in the right hypochondriac and lumbar region, which was pushing the IVC and right renal vein and showing associated lymphadenopathy. The patient had surgical resection of a well-defined encapsulated retroperitoneal tumor with dimensions of 16 × 12 × 9 cm with an attached cord-like structure of about ~10 cm. Histopathology revealed a spindle cell neoplasm with pleomorphism, necrosis, and mitoses (>5/10 HPF). Immunohistochemistry was positive for S-100, Sox10, and HMB45 with loss of SMA/Desmin/CD34. Diagnosis: Low-grade Malignant Peripheral Nerve Sheath Tumor (MPNST). Discussion: Retroperitoneal MPNSTs are extremely uncommon (<5% of soft tissue sarcomas). Imaging may raise suspicion of sarcoma, yet only histopathology and IHC can make a definitive diagnosis. Complete resection is still the mainstay of treatment. Prognosis is variable and depends on the size of the tumor, grade, extent of resection, and NF1 association. Conclusion: The diagnostic difficulty of retroperitoneal MPNST is brought out in this case and the need for a multidisciplinary evaluation involving imaging, histopathology, and immunohistochemistry.