MIB-1 EXPRESSION AND IODODEOXYURIDINE LABELING IN SOFT-TISSUE SARCOMAS - AN IMMUNOHISTOCHEMICAL STUDY INCLUDING CORRELATIONS WITH P53, BCL-2 AND HISTOLOGICAL CHARACTERISTICS

We investigated the relationship between immunohistochemical estimates of proliferative activity and expression of bcl-2 protein and mutant p53 protein in 23 cases of soft tissue sarcoma. Furthermore, the repro ducibility of estimates of proliferative activity was analysed and cor relations between the variables and with mitotic score were investigat ed. Proliferative activity was assessed by use of monoclonal antibody MTB-1 and staining for iododeoxyuridine (IdUrd), and evaluated in mult iple, random, systematically sampled fields of vision. MIB-1 indices w ere higher than those of IdUrd but for each case the two values were p ositively correlated (r = 0.78). The MIB-1 index correlated positively with mitotic score (2P < 0.001) and malignancy grade (2P = 0.001). Th e intraobserver reproducibility of the MIB-1 and IdUrd indices were ex cellent (r = 0.98 and r = 0.90, respectively), p53 expression was dete cted in 43% and strong bcl-2 expression was present in 57% of the stud ied cases. Expression of p53 and bcl-2 were not significantly correlat ed to proliferative activity or the histological features. We conclude , that the MIB-1 index is a reliable and reproducible estimate of prol iferative activity and might improve the accuracy of conventional mali gnancy grading of soft tissue sarcomas. Furthermore, the results indic ate that neither mutant p53 protein nor bcl-2 oncogene alone are suffi cient to induce increased proliferation in these sarcomas.