Malignant peripheral nerve sheath tumour (MPNST) are rare, aggressive sarcomatous tumours of peripheral nerve sheaths which can arise from preexisting neurofibroma or de novo.Sporadic origin accounts for nearly half of all MPNST cases,while other cases occur in association with neurofibromatosis type 1 (NF1).The most common site is nerve trunks of extremities like sciatic nerve. On literature search only four case reports of MPNST of radial nerve are published till date.We report a case of 50 years old lady presenting with a large,firm,ovoid swelling measuring 7 cm x 8 cm over her right arm with symptoms of neuropathy.The fine needle aspiration cytology report was a benign neurogenenic tumour. MRI reported as a radial nerve sheath tumour. Core biopsy shows features of neurofibroma(NF).She was subjected to treatment as a benign pathology but the final histopathological report was a low grade - malignant peripheral nerve sheath tumour.