Metastatic Breast Cancer Shows Different Immunohistochemical Phenotype According to Metastatic Site

AIMS AND BACKGROUND: The study was performed to assess the status of immunohistochemical markers in primary and metastatic breast cancer and to determine the organ-specific characteristics of metastatic breast cancer. METHODS: Samples from 13 cases of paired primary and metastatic breast cancer and 34 cases of metastatic breast cancer were included. RESULTS: In the analysis of 13 cases of paired primary and metastatic breast cancer, estrogen receptor and progesterone receptor loss were noted in 1 (7.7%) case each. Androgen receptor loss and gain was noted in 2 (15.4%) cases, respectively. HER-2 showed 100% concordance with primary and metastatic tumors. C-kit was demonstrated in only 2 (15.4%) cases of metastatic breast cancer. In the analysis of 34 cases of metastatic breast cancer, when classified into triple-negative type (ER-, PR-, and HER-2-), HER-2+ type, and ER+ or PR+/HER-2- type according to immunohistochemical stain results, HER-2 type (66.7%) in brain metastasis and ER+ or PR+/HER-2- type (75.0%) in liver metastasis were predominant. Bone metastasis was composed of triple negative type (44.4%) and ER+ or PR+/HER-2- type (55.6%), and lung metastasis showed all of three subtypes in similar proportions. CONCLUSIONS: Metastatic breast cancer shows different immunohistochemical phenotypes according to metastatic site (P = 0.048).