Image Findings of Polyostotic Fibrous Dysplasia Mimicking Metastasis in F-18 FDG Positron Emission Tomography/Computed Tomography

Fibrous dysplasia (FD) of the bone is characterized by the medullary cavity of bones becoming filled with fibrous tissue, and its etiology remains unknown. It is usually asymptomatic and found incidentally on imaging studies that are performed for other purposes. FD may closely mimic the appearance of bony metastatic disease on radiological examinations. We report the case of a 45-year-old female patient, which appeared to have multiple bone lesions on initial workup images. Subsequently, the bone lesions that showed increased FDG uptake on PET/CT in right femur and tibia were identified as FD. The present case is a useful addition to the current body of literature of false positive F-18 FDG PET/CT due to a benign skeletal pathology and underscores the importance of high index of suspicion and careful correlation, whenever one comes across such an unusual PET/CT finding.