COMPARISON OF P53 AND MIB1 EXPRESSION IN BENIGN AND BORDERLINE AREAS OF OVARIAN SEROUS TUMORS

Ovarian serous tumors of borderline malignancy frequently show morphol ogically benign and borderline areas within the same tumor. This study was undertaken to determine if these two morphologically disparate ar eas differ in their proliferative activity and p53 expression. Formali n-fixed, paraffin-embedded archival tissue from 17 ovarian serous bord erline tumors with morphologically benign and borderline areas were im munostained with monoclonal antibodies against p53 and MIBI. The perce ntage of positive cells was determined by counting 100 consecutive cel ls for each stain in the most intensely stained areas in morphological ly benign and borderline portions of these tumors. There was a signifi cantly increased proliferation (MIB1 expression) in borderline areas c ompared with benign areas (37.05 +/- 15.3 versus 12.88 +/- 6.7, p = 0. 0001). More than 30% of cells were positive for MIB1 in 13/17 borderli ne areas compared with none of the 17 benign areas (p < 0.0001). The e xpression of p53 was also higher in borderline areas compared with ben ign areas (7.12 +/- 8.8 versus 2.94 +/- 4.46, p = 0.0078). More than 1 0% of cells were p53 positive in 5/17 borderline areas compared with 1 /17 benign areas (p = 0.08). However, there was no significant correla tion between p53 expression and MIB1 expression in either the benign o r borderline areas (p = 0.4 and 0.2, respectively). In summary, morpho logically borderline areas show significantly higher p53 expression an d proliferation compared with morphologically benign areas in ovarian serous borderline tumors. Alterations of p53 may play a pathogenetic r ole in some ovarian serous borderline tumors. The lack of correlation between p53 expression and MIB1 expression, however, suggests involvem ent of other factors, in addition to p53, in determining the prolifera tive rate of ovarian serous borderline tumors.