False Positive FDG PET/CT Resulting from Fibrous Dysplasia of the Bone in the Work-Up of a Patient with Bladder Cancer: Case Report and Review of the Literature

Abstract

Fibrous dysplasia of the bone (FDB) is a common, genetic, developmental disorder with a benign course. FDB can be seen anywhere throughout the skeleton. It is usually asymptomatic and found incidentally on imaging studies that are performed for other purposes. Although whole body 18 F-flourodeoxyglucose PET/CT (FDG PET/CT) is widely used in tumor imaging, infections and benign pathologies like FDB may cause false positive results. Herein we report the case of a 48-year-old FDB patient with transitional cell carcinoma of the urinary bladder. Restaging FDG PET/CT showed multiple mild to moderate hypermetabolic bone lesions which were initially misinterpreted as bone metastases. In this case report, we aimed to guide physicians in evaluating bone lesions in cancer patients with FDB in the light of the literature.

Giant Polyostotic Fibrous Dysplasia: F-18-flourodeoxyglucose Positron Emission Tomography/Computerized Tomography and Radiologic Findings

“…In tibia, when originates in cortex, FD is indistinguishable from adamantinoma. This distinction can be made pathologically (5,11,12,14). enlargement of medulla, deformity with endosteal thinning, increased trabeculation to a characteristic "ground-glass" appearance which is formed by a mixture of immature bone and fibrous tissues (2,4,8).…”

“…CT is still the best technique for delineating the extent of involvement with the typical ground glass pattern of the bone. The lesion is surrounded by a reactive sclerotic bone (5,14).…”

“…The diagnoses of FD and its complications are based on physical, radiological, and histopathological examination. The use of the whole body F-18-flourodeoxyglucose (FDG) positron emission tomography/ computed tomography (PET/CT) imaging is not rare because FD shows various FDG uptake and can mimic multiple bone metastases, especially in polyostotic form (5,6).…”

PET/CT in Benign and Malignant Musculoskeletal Tumors and Tumor-Like Conditions

“…misinterpreted as bone metastasis in cases with intense FDG uptake. 42,43 FDG uptake in fibrous dysplasia may change 44 according to the patient's condition or changes in lesion characteristics (►Fig. 18).…”

Fibrous dysplasia mimicking vertebral bone metastasis on 18F-FDG PET/computed tomography in a patient with tongue cancer

“…Fibrous dysplasia is a benign and slowly progressive disorder in which normal bone is replaced by abnormal fibroosseous tissue [1]. The ribs, femur, tibia, calvarium, long bones, spine, and pelvis are the most frequently involved sites in FD [2].…”