ERBB2 and breast carcinoma: 2021). It acts as a negative prognostic factor. It has been recommended by the American Society of Clinical Oncology (ASCO) for use in treatment monitoring and prognostic evaluation in hormone receptor–positive breast cancer (HBC) (Ross et al. 2016). HER‐2 over‐expression in HBC is associated with higher tumour aggressiveness, poor therapy response and shorter survival time. In breast carcinoma, samples obtained by fine needle aspiration can be used to evaluate the expression of HER (Wolff et al. 2013).