Expression of c-erbB-2 gene product and hormone receptor status in phyllodes tumors and fibroadenomas: An immunohistochemical study

Background: The histogenesis of phyllodes tumors and fibroadenomas appear to be closely related. Although fibroadenoma is thought to be an entirely benign breast tumor, the histological characteristics of phyllodes tumors do not often not correlate with clinical outcome and objective criteria in categorizing the grade of malignancy in phyllodes tumors is still controversial. The goal of this study is to investigate whether the expression of c-erbB-2 oncoprotein, estrogen receptor and progesterone receptor proteins correlates with the biological behavior of these tumors. Methods: The expression of the proteins was investigated using immunohistochemistry in 21 female phyllodes tumor and 27 fibroadenoma patients. The cases of phyllodes tumors were categorized into three groups: (malignant, four cases; borderline, eight and benign, nine). Results: Expression of c-erbB-2 protein was found in 14 cases of phyllodes tumors (66.6%) and four fibroadenoma patients (14.8%). There was statistically significant difference between phyllodes tumor and fibroadenoma, as well as among the three categories of phyllodes tumors (p<0.0001 and p=0.001, respectively). Estrogen receptor expression was detected in nine cases of phyllodes tumors (42.9%) and 11 fibroadenoma patients (40.7%), whereas 19 of phyllodes tumors (90.5%) and 16 of fibroadenomas (59.3%) showed Progesterone receptor expression. Statistical analysis revealed a significant difference of only Progesterone receptor expressions between phyllodes tumor and fibroadenoma (p=0.02), however hormone receptor status did not appear to be a significant criterium by which to categorize the grade of malignancy in phyllodes tumors. Conclusion: Our study suggests that overexpression of c-erbB-2 protein correlates with increasing grade of malignancy in phyllodes tumors and a hormone-dependent stimulation plays a role in tumorigenesis of this tumor suggesting the possibility of effective endocrine therapy