Low Grade Osteosarcoma
(also termed well differentiated intramedullary osteosarcoma)
     Low Grade Osteosarcoma accounts for 1-2% of osteosarcomas. This intraosseus tumor occurs in the metaphysis and diaphysis of the distal femur or proximal tibia. Low grade osteosarcoma occurs in an older patient population than conventional osteosarcoma and presents more often as a pathologic fracture.
     On plain x-ray, low grade osteosarcoma may appear as osteolytic, ground glass, or sclerotic. The bone destruction is regular and expansive which often contributes to a misdiagnosis as benign. This slow growing tumor has poorly defined margins.
     Low grade osteosarcoma is normally a grade 1 tumor histologically. There is a large amount of collagen surrounding the occasional spindle cells. Some authors believe this tumor is a relative of parosteal osteosarcoma as they both have a similar microscopic appearance and low malignant potential.
     Like parosteal osteosarcoma, low grade osteosarcoma has a good prognosis. Treatment is surgical excision and is not followed by chemotherapy.

Bloem, JL and HM Kroon, Osseous Lesions, Radiologic Clinics of North America, 31(2):261-277, March, 1993.

Bullough, Peter, Orthopaedic Pathology (third edition), Times Mirror International Publishers Limited, London, 1997.

Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis, W.B. Saunders, Co., 1991.










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