IMMUNOHISTOCHEMICAL PROFILE OF PHYLLODES TUMORS OF THE BREAST

The immunohistochemical profiles of 16 cases of phyllodes tumor of the breast (9 benign and 7 malignant) from 15 patients were examined by t he labeled streptavidin biotin method. The expression of Ki-67, p53, b cl-2, alpha-smooth muscle actin (alpha-SMA), desmin, S-100 protein, es trogen receptor (ER), and progesterone receptor (PgR) was analyzed. Th e number of Ki-67-positive stromal cell nuclei of malignant phyllodes tumor were significantly more prominent than the benign tumors. The p5 3 expression on the stromal cell nuclei showed a significant differenc e between malignant and benign cases (86% vs 22%; p<0.05). bcl-2 was r egularly seen on the luminal cell cytoplasm and stromal cell labeling showed no significant difference between malignant and benign cases (2 9% vs 33%). Stromal cells were alpha-SMA positive but refractory among cases, and desmin and S-100 protein were negative. PgR was expressed in all 16 cases and ER in most cases (12/16) the expression of which w as restricted to luminal epithelial cell nuclei. These findings indica te that the Ki-67 labeling index and p53 expression in the stroma woul d be a good diagnostic parameter distinguishing benign tumors from mal ignant tumors. However, the absence of steroid receptor expression in stromal cells suggests the ineffectiveness of hormonal therapy for phy llodes tumor of the breast.