A Multifocal Malignant Fibrous Histiocytoma of the Bone Evolving From Fibrous Dysplasia

Fibrous Dysplasia (FD) is a focal bone lesion occurring sporadically and in hereditary syndromes caused by activating mutations of the G protein alpha subunit. It rarely undergoes malignant transformation. Malignant Fibrous Histiocytoma (MFH) is a sarcoma of soft tissues and may be found as primary sarcoma of the bone or multifocally. Until now only a few cases of malignant transformation of FD into MFH of the bone have been described. We report a case of a 38 year old female with polyostotic FD. Years after the first diagnosis of FD, pain with sudden onset and diminution of force in the left lower limb finally led to the diagnosis of a multifocal MFH of the bone. No response to different chemotherapy schemes was found and the patient deceased shortly after. This is the first described case of a polyostotic FD with malignant transformation into a multifocal MFH of bone. Due to the rarity of this entity and the lack of response to chemotherapy no treatment recommendations can be concluded.