The aims of this study were to determine the diagnostic accuracy of CT-guided bone lesion biopsy for the confirmation of bone metastases in patients with breast cancer, to identify variables which influence the quality of the histopathological specimen and to examine if estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) status of the metastasis differs from the immunohistochemical status of the primary tumor. The gene discussed is ESR1; the disease is breast cancer.