In the TCHL clinical trial (NCT01485926), which assessed TCH (docetaxel, carboplatin, and trastuzumab) and TCHL (TCH and lapatinib) in stage II-III HER-2-positive breast cancer patients, we obtained core biopsy samples from the primary tumour from consenting patients at pretreatment and at 20-days post-cycle 1 of trastuzumab-based treatment. The gene discussed is ERBB2; the disease is breast cancer.