PHYLLODES TUMOR OF THE BREAST - IMMUNOHISTOCHEMICAL STUDY OF 37 TUMORS USING MIB1 ANTIBODY

In our study, the expression of Ki-67 antigen in phyllodes tumours of the breast was investigated in order to estimate its significance in a ssessing the grade of malignancy and in predicting the clinical behavi our of these rumours. Formalin-fixed and paraffin-embedded tissue spec imens of 37 cases of phyllodes tumour of the breast (eight graded as m alignant and 29 as benign according to histopathological criteria) and 20 breast fibroadenomas were stained by an immunoperoxidase technique , using the monoclonal antibody MIB1 directed against cell proliferati on-associated Ki-67 antigen. A MIB1 index was calculated to express th e percentage of MIB1 positive proliferating stromal cells. Our data in dicate that there are statistically significant differences in MIB1 in dices between histologically benign and malignant phyllodes rumours (a lpha = 0.001), between benign phyllodes tumour and fibroadenoma (alpha = 0.01), and between malignant phyllodes tumour and fibroadenoma (alp ha = 0.001). Our results also indicate a good correlation between the conventional grading of phyllodes tumours based on histological criter ia and MIBI indices. However, little predictive value of the MIB1 inde x in phyllodes rumours of the breast can be derived from our study.