In breast tumours, PIK3CA mutations have been consistently associated with ER-positive and human epidermal growth factor receptor-2 (HER2)-positive tumour status (Saal et al, 2005; Li et al, 2006; Perez-Tenorio et al, 2007; Stemke-Hale et al, 2008) (Saal et al, 2005; Perez-Tenorio et al, 2007). The gene discussed is ERBB2; the disease is breast neoplasm.