Utility of Ki-67, CD10, CD34, p53, CD117, and mast cell content in the differential diagnosis of cellular fibroadenomas and in the classification of phyllodes tumors of the breast.

Adequate management of phyllodes tumors of the breast (PTB) remains a challenge because of the difficulty in correctly establishing preoperative diagnosis. The aim of this study was to evaluate the usefulness of Ki-67, CD10, CD34, p53, CD117, and of the number of mast cells in the differential diagnosis of benign PTB and cellular fibroadenomas (CFs) as well as in the grading of PTB. Fifty-one primary PTB and 14 CFs were examined by immunohistochemistry.When evaluating CD117 expression, higher epithelial expression was present in CF as well as an increased number of mast cells in benign PTB. Stromal expression of Ki-67, CD10, CD34, and p53 were relevant to PTB grading, of which the first 3 showed significance in the distinction of benign and borderline PTB, as well as between benign and malignant PTB. P53 was relevant only for the discrimination between benign and malign PTB. None of the markers showed significance in distinguishing between borderline and malign PTB.