Six out of 46 osteosarcomas wereassociated with 100%, chemotherapeutically induced tumor necrosis, and in 3 casesthe post-chemotherapy specimens could not be immunohistochemically evaluated.In the former 6 osteosarcomas, the corresponding Pgp expression in thepre-chemotherapy, diagnostic biopsies showed a score of 1 (i.e., chemotherapy sensitivity) in 4 cases, score 2 (chemotherapyresistance) in one case, and for the remaining case the pretreatment biopsycould not be evaluated for technical reasons. This evidence concerns the gene PGP and neoplasm.