Abstract

Well differentiated osteosarcomas are variants of osteosarcoma composed mainly of fibrous and osseous tissue with minimal cystologic atypia. This tumor may be misinterpretated as a benign lesion if the radiologic and clinical features are not taken into account. We report a typical case of intraosseous well differentiated osteosarcoma occuring in the left distal femur of a 58-year-old woman. Radiologically, it appered as an ill-defined lesion with a mixture of sclerotic and osteolytic ares. But there was a lack of highly destructive appearance of conventional osteosarcoma. Grossly, the mass occupied a metaphysis of the distal femur with extension into the diaphysis and epiphysis. Multifocal cortical destruction and sclerosis were also associated. Histologically, the mass showed typical features of intraosseous well differentiated osteosarcoma. There were various patterns of osteoid deposits and bone formation mimicking those of fibrous dysplasia, nonossifying fibroma or parosteal osteosarcoma.

• Keywords: Bone tumor;Well differentiated osteosarcoma;Low grade osteosarcoma;Femur;