Despite the rate of distant metastases not being related to tumour grade or BC subtype, which has also been found by other studies [14, 37, 43], the location of metastases differed according to primary tumour subtype (for example, triple negative and HER2 + tumours had more extra-skeletal metastases than ER + /HER2 − tumours) [37]. Here, ERBB2 is linked to breast cancer.