Significance of epidermal growth factor receptor expression in the grading of phyllodes tumors of the breast

Background and aim: Limited studies on the relationships between epidermal growth factor receptor (EGFR) expression and the grades of phyllodes tumors (PT) of the breast were reported. This study evaluated the significance of EGFR overexpression in the grading of PT. Methods: Immunohistochemical stain for EGFR was done in 46 PT cases. The differences of EGFR expression according to the degrees of cytologic atypia and mitotic count and between benign, borderline and malignant PTs based on Rosen or World Health Organization (WHO) criteria were analyzed. Results: Significant differences of positive (moderate membranous and cytoplasmic, more than 10% of tumor cells) and strong positive (moderate more than 50% of tumor cells) reactions for EGFR were found according to the degree of cytologic atypia (P= 0.0016 and P= 0.0122) and between the PTs showing ≤5 mitoses and >5 mitoses/10 high power field (P= 0.0230 and P= 0.0058). Positive reaction for EGFR was more common in borderline/malignant PTs than benign PTs, and strong positive reaction for EGFR was relatively common in malignant PTs. Conclusions: Epidermal growth factor receptor overexpression, more than 10% of tumor cells, could be used as an ancillary tool for the discrimination of benign from borderline and malignant PTs.