Prognostic evaluation of proliferative activity and DNA content in the phyllodes tumor of the breast: immunohistochemical and flow cytometric study of 118 cases

The goal of this study was the prognostic evaluation of histology, mitotic rate, S-phase fraction (SPF) and expression of proliferative antigen Ki67 and p53 protein in phyllodes tumor of the breast. The study was performed in the group of 118 patients with phyllodes tumor treated by surgery from 1952 to 1998. Mitotic rate was assessed on the representative histological specimens. Expressions of Ki67 and p53 were evaluated by immunohistochemistry on a section from the corresponding paraffin blocks which were also used for flow cytometric DNA evaluation. Histologically, 52 tumors were benign (LGM), 24 borderline malignancies (BM) while among 42 malignant tumors, 20 were monomorphous (HGM) and the remaining 22 revealed heterologic elements (HGH). Tumor recurrencies occurred in 17 patients, predominantly during the first three years after surgery, and 13 patients died of the tumor (1 BM, 12 both malignant variants). Multivariate analysis demonstrated mitotic rate, SPF and p53 expression as independent prognostic parameters for the disease-free survival. Histological tumor type and expression of Ki67 influenced independently the overall survival. In conclusion, the histological type of tumor phyllodes forms the basis for the prognosis of clinical outcome, but the indicators of the proliferative activity, especially Ki67 index, are valuable prognostic factors among patients with malignant variant of phyllodes tumor of the breast. Expression of the p53 protein in tumor cells could be also useful when the percentage of cells and intensity of expression are considered.