Although fibrous dysplasia is not considered a potentially premalignant disorder, malignant transformation occurs. Because of its rarity, radiographic features of malignantly transformed fibrous dysplasia on cross-sectional imaging modalities are less recognized, making diagnosis and differential diagnosis of the disease quite difficult in clinical practice. In this study, we analyzed the clinical characteristics, imaging features, pathology findings and surgery strategies of 19 malignantly transformed fibrous dysplasia. We found that there was significant male predominance in this specific cohort (13/6). While osteosarcoma (63.2%) was the most frequently occurring neoplasm secondary to fibrous dysplasia, other less commonly malignantly changed types included fasciculated sarcoma, malignant fibrous histiocytoma, fibrosarcoma and chondrosarcoma. We found that the diagnostic value of single modality imaging method, like conventional X-ray, computed tomography or non-contrast magnetic resonance imaging, was limited mainly because of a lack of whole-body metabolic information. In contrast, we highlighted that 99mTc-MDP SPECT/CT and/or 18F-FDG PET/CT scanning could exert a pivotal role in the management of malignantly transformed fibrous dysplasia by guiding precise biopsy and optimizing surgery options.
Keywords: Fibrous dysplasia; fibrosarcoma; malignant transformation; nuclear medicine imaging; osteosarcoma.