Parosteal (juxtacortical) Osteosarcoma of the Distal Femur

Abstract

Summary Parosteal osteosarcoma is a very rare primary bone tumor which most frequently inolves thepopliteal fossa.The tumor is situated at the outer suface of the cortex of the bone, where it surrounds the bone like concentric shells.The case of a 21-year-old woman with a parosteal osteosarcoma of the left distal femoral metaphysis is presented.The tumor shows the typical radiological features of this unusual lesion with dense tumor masses surrounding the distal femur.The tumor could not be removed completely at the first operation.One year later a recurrence was noted, and during this period the tumor had increased considerably in size. This very rare lesion usually presents great diagnostic and differential diagnostic difficultieswith regard to the interpretation of its histological pattern, which does not suggest a malignant growth.In the case presented here, intraosseous sclerosis of the distal femoral metaphysis was a remarkable radiological feature which raised the question as to whether or not the tumor had already invaded the femoral cavity.This observation is of decisive importance in adopting an appropriate therapy.