ERBB2 and bone metastasis: Half of these studies [49,51,77,79] reported detailed demographic and clinical–pathological information such as age of primary diagnosis of breast cancer and bone metastasis, primary breast cancer histology, hormone receptor (estrogen, progesterone) and HER2 condition, breast cancer molecular subtype, sites of metastases at breast cancer presentation, if metastatic, or at time of recurrence, date and site of disease recurrence, date of bone progression, and date of skeletal-related events (SREs), while the other half reported less or no information on derived patient fluids or tissues.