Monostotic Fibrous Dysplasia Mimicking Metastasis in the Femoral Neck on Bone Scintigraphy and 18F-FDG PET/CT.

A 51-year-old woman who had lung adenocarcinoma was found to have a high uptake area over the right femoral neck by means of bone scintigraphy, suggesting a suspicious bony metastasis. 18F-FDG PET/CT was arranged, and showed an FDG-avid lesion in the same region. However, after augmented CT, a well-defined ground-glass lesion with circular calcification was found, which is the favored benign lesion of fibrous dysplasia. The following imaging of bone scintigraphy and 18F-FDG PET/CT presented no apparent change. This case demonstrates that the treatment scheme should not be solely guided by abnormalities in scintigraphy. Additional imaging is recommended for accurate staging or development of an appropriate treatment plan.