Periosteal osteosarcoma - personal experience with five cases

The authors present five cases of periosteal osteosarcoma located in the femur (4) and tibia (1) in children and young adults (1 female and 4 males) with an age range of 9 - 23 years (mean age 15 years). Radiographs in all cases showed a broad-based soft tissue mass attached to the cortex with periosteal reaction and in two of them cortical disruption with extensive medullary involvement. Follow-ups were available in four cases (range 11 - 73 months) and revealed pelvic metastasis after 15 months with ultimately rapid dissemination and death in a 9-year-old girl and metastasis to the humerus after 13 months in a 15-year-old boy. The former tumor widely extended into the medullary cavity and an amputation was carried out, the latter had a pure juxtacortical position and an en block resection was performed; both of them were treated with chemotherapy. All the lesions displayed distinctive structural patterns combining a large island of tumorous cartilage and hypocellular, bland-looking myxoid mesenchymal stroma with abrupt transition between both components. Contrary to conventional osteosarcoma, the delicate flocculent osteoid deposits were produced by innocuous stromal cells lacking apparent atypia. They were strictly situated outside the prevailing chondroid areas and disclosed sometimes only after a meticulous search. Immunohistochemical detection of SATB2, S100protein and D2-40 assisted effectively not only in recognition of the real stromal histogenetic derivation, but also in distinction of true differentiation of a heavily mineralized extracellular matrix. Molecular analysis revealed no IDH1/2 mutation in four examined cases. Regardless of unique low-grade morphology in rare periosteal osteosarcoma, an aggressive therapeutical approach similar to conventional osteosarcoma is justified, particularly in the case of a medullary extension.