Phyllodes tumor of borderline malignancy: seven year follow up with immunohistochemical study.

The patient was 80 years old when she initially presented with a left breast mass. Originally, a needle biopsy showed benign stromal and ductal cells. Five years later, the breast mass increased in size and a core needle biopsy showed a biphasic intraductal papillomatous tumor with cellular stroma. Eighteen months later, another biopsy was taken from the breast mass, revealing a well-developed phyllodes tumor (PT) of borderline malignancy. One month later, a simple mastectomy was performed for this 87-year-old woman. Histolopathologic and immunohistochemical studies, including estrogen and progesterone receptors, Ki-67 and p53, performed on tissues from the different biopsy specimens confirmed the progressive transition of the tumor in a 7 year period. An increase in mitotic activity was noted in the later samples. Similarly, percentages of p53- and Ki-67-positive cells were much higher in the stromal and ductal cells of the later samples compared to the original specimen. These findings support the notion that Ki-67 and p53 immunohistochemical staining may be used as simple and practical markers for the evaluation of the malignant potential of PT.