OBJECTIVETo compare two different methods, namely orthotopic implantation and armpit implantation, for establishing nude mouse model bearing osteosarcoma in light of the tumor formation rate and time, tumor growth changes and lung metastasis.

METHODSOsteosarcoma cells were inoculated in the left armpit or the femoral medullary canal of nude mice, and the tumor growth was observed 6 weeks later. The differences in the pulmonary metastasis were examined macroscopically and microscopically.

RESULTSArmpit implantation allowed easy operation and fast tumor growth, but tumors often sustained damages by frictions on the surface (P<0.05), and avascular necrosis occurred earlier in the tumors (P<0.05). With this approach, the pulmonary metastasis rate was only 40% (P<0.05), and the metastases in the lungs were sparser (P<0.05) and small. Orthotopic transplantation could well simulate the original growth environment of osteosarcoma, and resulted in milder avascular necrosis and greater pulmonary metastasis rate (100%) with larger and denser metastatic foci. But orthotopic transplantation required more complicated operation for establishing osteosarcoma-bearing models.

CONCLUSIONThe two methods both result in high tumor growth rate, but orthotopic transplantation is superior in inducing pulmonary metastasis of osteosarcoma and reducing friction injury of the tumor and avascular necrosis in the tumor.