Little prospective information is available in T1a/b tumors, and only the Breast Cancer International Research Group 006 trial (BCIRG-006) allowed inclusion of node-negative tumors < 10 mm.6 However, with reported 5-year distant recurrence–free survival of 98% in untreated HER2-positive T1a/b tumors,30 the benefit from adjuvant chemotherapy and trastuzumab is possibly outweighed by the toxicity of treatment31 in this subgroup of patients. This evidence concerns the gene ERBB2 and breast cancer.