- AIMS: The treatment of bone metastases in breast cancer is traditionally based upon the receptor status of the primary tumour. However, retrospective studies have shown significant discordance in receptor expression between primary and metastatic tumours. Therefore, the aim of this study was to prospectively assess the incidence of discordant receptor status in primary and metastatic disease and evaluate the role of bone marrow biopsies for the reassessment of receptor status. MATERIALS AND METHODS: Nine patients with known bone metastases were assessed with both a radiologically guided bone biopsy and a bone marrow aspirate and trephine. The oestrogen receptor and progesterone receptor status of these samples was assessed and compared with the primary breast cancer. Bone and bone marrow samples were also evaluated for HER2/neu status and compared with the status of the primary tumour if available. RESULTS: Tumour cells were found in six of the nine bone metastasis specimens and five of the nine bone marrow samples. A discordance rate for the oestrogen receptor was seen in five of nine patients (56%) and for the progesterone receptor in four patients (44%). There seemed to be a correlation between bone and bone marrow biopsies. CONCLUSION: The receptor discordance rate in this study was similar to previous retrospective studies. It seems that bone marrow biopsy may be a simple, safe and well-tolerated way to obtain tissue to reassess the receptor status of metastatic breast cancer.