AgNOR, Ki-67 and PCNA expression in fibroepithelial tumours of the breast in correlation with morphological features

The authors retrospectively reviewed the cytological slides of 44 histopathologically confirmed fibroepithelial lesions of the breast, of which 11 were fibroadenoma (FA), 19 benign phyllodes tumours (PTLGM), 8 borderline (PTBM) and 6 malignant (PTHGM). The 2 FA misdiagnosed as PTLGM in cytological smears were both of cellular type. NORS were quantified in a series of the above cases using the silver-colloid method. Expression of Ki-67 and PCNA were evaluated by immunohistochemistry on sections from the corresponding paraffin blocks. The results were compared with morphological parameters. In phyllodes tumours (PT), the AgNOR scores showed a tendency to increase with degrees of malignancy. There was significant correlation between AgNOR counts and proliferation rates as determined by Ki-67 and PCNA immunostaining. Ki-67 and PCNA expression correlated with mitotic count, stromal overgrowth, cellularity and atypia in PT. Determination of the AgNOR number per cell revealed an overlap between FA and PTLGM. The proliferating activity determined by immunohistochemistry with Ki-67 and PCNA antibodies did not reveal any significant difference between FA and PTLGM. In summary, Ki-67 and PCNA expression is suggested as a marker of stromal element proliferation. The results obtained confirm the diagnostic difficulties in distinguishing PTLGM from FA of the cellular type using fine needle aspiration cytology.