HER2 FISH analysis on a skeletal metastasis: a case report and technical review

Eighty per cent of patients who develop metastatic breast cancer will experience a skeletal metastasis. National guidelines recommend biopsy and repeat estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2) testing for all metastatic breast cancers to guide further treatment planning. Biomarker analysis in bone biopsy samples is challenging due to the necessity of decalcification of the bone sample in order to allow tissue sectioning. The decalcification solutions may result in the degradation of proteins and thus affect the results of immunohistochemical (IHC) testing for ER, PR, and HER2. The decalcification solutions may also degrade nucleic acids, and result in poor or no hybridization signals when attempting in situ hybridization (ISH) testing for HER2. Here, we report a patient with metastatic breast cancer to the bone who underwent image guided core needle biopsy. Her past medical history was significant for ER+, PR+, and HER2+ breast cancer. The bio...