Abstract: Objective To investigate the effects of wax surface deca-lcification on osteosarcoma morphology and molecular biology. Met-hods 17 specimens of osteosarcoma were collected, Two pieces of bone tissue containing tumor were cut out and divided into two gr-oups: surface decalcification group and routine decalcification group,the paraffin sections were stained with HE; Immunnohistochemical Staining was used to detected the expression of Ki-67,statb2,caspase9, su-rvivin and BAX; Fluorescence in situ hybridization with MDM2 probe was used to detected the gene amplification; Results There was no difference between the surface decalcification group and the routine decalcification group on HE staining，The differenceof antigen expression and MDM2 gene amplification was significant Conclusions The surface decalcification of wax block is superior to the routine decalcification in morphology,antigen and preservation of antigen and nucleic acid.

Key words: surface decalcification, osteosarcoma, morphology, immunohistochemistry, FISH