Intraosseous malignant peripheral nerve sheath tumor of distal femur detected with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging

Malignant peripheral nerve sheath tumor (MPNST) is a malignant soft tissue tumor arising from peripheral nerve sheath cells. MPNST is uncommon and can be associated with neurofibromatosis Type I (NF-I). MPNST involving bone is very rare, and we report the case of MPNST involving the distal femur in a patient without NF-I. A 17-year-old boy presented with a history of left knee joint pain and X-ray showed lytic lesion in the distal part of left femur. He was referred for fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) to find out the extent of disease. PET/CT showed intense FDG uptake in the lobulated well-defined lesion in the medial part of left distal femur. He underwent biopsy from the lesion which confirmed MPNST.