RESUMO
Fibrocartilaginous dysplasia has been described as a rare variant of fibrous dysplasia. This lesion will appear in imaging as ground glass matrix similar to fibrous dysplasia, but it will also show rings and arcs calcifications. In turn, this can lead to misdiagnosing fibrocartilaginous dysplasia as primary cartilaginous lesion such as enchondroma or chondrosarcoma, neccesating histopathological confirmation. We report a case of fibrocartilaginous dysplasia in a 19 years old male with polyostotic fibrous dysplasia with prior pathologic fracture of the left femur. The patient presented with progressive swelling of the left thigh, imaging was done and showed enlargement of the fibrous dysplasia in the left femur with new rings and arcs matrix mineralization. The lesion was biopsied and microscopic evaluation revealed mainly cartilage islands with fibro-osseous tissue. We also discuss the possible origin of the cartilaginous component in this lesion, and its clinical course.