Immunohistochemical assessment of primary breast tumors and metachronous brain metastases, with particular regard to differences in the expression of biological markers and prognosis.

In this study, we conducted an immunohistochemical analysis of primary breast tumors and metachronous brain metastases to compare the differences in the expression of biological markers between the two. Carcinoma tissues from primary breast tumors and metachronous brain metastases collected from 21 patients were examined immunohistochemically for the expression status of the estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor (HER)-2, Ki-67, bcl-2 and p53, and the results were compared. In addition, the relationships between the expression of these factors and prognosis were evaluated. There were no significant differences in the frequencies of ER-, PgR-, HER-2-, bcl-2- or p53-positivity between the primary breast tumors and metachronous brain metastases. While the Ki-67 labeling index (LI) was high in both the primary breast tumors and brain metastases, it was significantly higher in the brain metastases than in the corresponding primary breast tumors (P=0.003). With regard to the prognosis, breast cancer patients who showed ER-positivity in the primary tumors showed significantly longer survival after primary diagnosis (P=0.0076). Furthermore, breast cancer patients who exhibited ER-positivity, bcl-2-positivity or p53-negativity in the primary tumors showed significantly longer intervals from primary diagnosis to the detection of the brain metastases. Of all the markers, only the Ki-67 LI was significantly higher in the brain metastases than in the primary breast tumors. We confirmed that the tumor characteristics were worse in the metachronous brain metastases.