Malignant peripheral nerve sheath tumor presenting as pathological fracture of femur in neurofibromatosis patient

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas that arise from a peripheral nerve or cells associated with the nerve sheath, such as Schwann cells, perineural cells, or fibroblasts. MPNSTs account for 5%–10% of all soft tissue sarcomas. Neurofibromas in Neurofibromatosis-1 (NF-1) may undergo malignant transformation in 2%–5% of patients. We are reporting a very rare case in NF-1 patient who, presented with pathological intertrochanteric fracture of femur and liver metastasis. X-ray from left hip joint shows lytic lesion which on histopathology turned out to be MPNST. S-100 was positive confirming its neural origin. Elbow lesion which was excised later, also showed similar features with S-100 positivity. Ultrasonography abdomen showed target lesions in liver. Fine-needle aspiration cytology from liver showed scattered malignant spindle cells. A final diagnosis of metastatic MPNST was made. Although malignant transformation in neurofibromas is extremely rare when it occurs, it is associated with NF-1 in 75% of patients. This case highlights the possibility of fracture femur as the presenting complains, in patients of NF with malignant transformation. The case is unique with regard to its presentation and rarity of metastatic sites.