[Mazabraud syndrome--benign intramuscular myxoma with fibrous skeletal dysplasia].

A 51-year-old woman presented with a soft-tissue swelling of the thigh. A MRI scan of the thigh showed an intramuscular lesion and bone-marrow abnormalities in the femur. A bone scintigraphy and PET/CT-scan showed multiple hotspots in the skeleton. The soft-tissue swelling was excised. Although we initially suspected a malignancy of the thigh with diffuse skeletal metastases, this proved to be a benign myxoma which, together with the skeletal abnormalities, corresponded with a diagnosis of Mazabraud syndrome. This is a rare benign disorder in which intramuscular myxomas are associated with fibrous dysplasia of the skeleton. In the case of asymptomatic fibrous dysplasia a conservative approach is sufficient. In the case of fibrous dysplasia associated with pain, or imminent fracture, a prophylactic surgical intervention is indicated. To avoid anxiety, unnecessary diagnostic procedures and surgery Mazabraud syndrome should be always be considered in the case of an intramuscular tumour associated with concurrent skeletal abnormalities.