p53 and c-kit (CD117) protein expression as prognostic indicators in breast phyllodes tumors: a tissue microarray study

Breast phyllodes tumors are fibroepithelial neoplasms whose clinical behavior is difficult to predict on histology. There is relatively scant data on the role of biological markers. In this study, we determined if p53 and CD117 (c-kit) protein expression was predictive of behavior in a series of 335 phyllodes tumors diagnosed at the Singapore General Hospital, using immunohistochemistry on tissue microarrays. Representative areas from 250 (75%) benign, 54 (16%) borderline and 31 (9%) malignant phyllodes tumors were selected for construction of tissue microarrays using the 2 mm punch. Immunohistochemistry for p53 and CD117 was carried out using the streptavidin–biotin method. Staining proportion and intensity of both epithelial and stromal elements were analyzed. p53 immunostaining was observed in the epithelium of 28 (10%) of 278 microarrays; myoepithelium of 53 (21%) of 251 microarrays; and stromal cells in 105 (36%) of 289 microarrays. CD117 immunohistochemical reactivity was noted in epithelial and stromal components of 175 (of 267, 66%) and 17 (of 273, 6%) microarrays, respectively. Stromal p53 and CD117 protein expression was associated with tumor grade (P