Immunohistochemical status of p53, mdm2 and Ki-67 in malignant fibrous histiocytoma.

The aim of the study was to evaluate the frequency of p53, mdm2 and Ki-67 immunopositivity in MFH, and to investigate possible associations of their expression with the grade of malignancy and predominant histological pattern--storiform, pleomorphic and myxoid subtype of MFH. A total number of 51 tumor samples from 21 primary and 30 secondary MFHs was studied using monoclonal anti-p53 (DO-78, DAKO), anti-mdm2 (1F2, NOVOCASTRA) and polyclonal anti-Ki-67 (DAKO) antibodies. The p53 immunopositivity was observed in 32.7% of all tumor samples (in 36.8% of primary and in 30% of recurrent and metastatic tumors). The mdm2 immunopositivity was noted in 34.8% of all tumor samples (in 33.3% of primary and 35.7% of secondary tumors). The mean percentage of p53, mdm2 and Ki-67 positive cells was 15.5, 8.8 and 7.05, respectively. The mean Ki-67 LI was statistically higher in grade 3 than in grade 2 of malignancy (p = 0.006). A significant correlation was found between mdm2 positivity and histological subtypes of MFH--storiform and pleomorphic types were more frequently mdm2 positive than myxoid variant (p = 0.035 and p = 0.009, respectively). No such correlation was observed for p53 positivity of tumors and subtypes, but there was a statistically significant difference in the percentage of p53 positive cells between storiform and myxoid type (p = 0.049). We also noted more tumors expressing high percentage (over 20%) of mdm2 positive cells in pleomorphic and storiform subtypes than in myxoid variant (p = 0.048). The Ki-67 LI was also higher in pleomorphic than in other types of MFH (p = 0.012). A strong positive correlation was found between p53 positivity and mdm2 positivity of tumors in primary MFHs (p = 0.00146). p53 and mdm2 positive tumors were mainly in grade 3 of malignancy, but no statistically significant correlations were noted. A positive correlation between the percentage of p53 positive cells and Ki-67 positive cells (p = 0.0028) was observed.