The MHS eligibility criteria for testing included ER+ N0/pN1mic invasive tumours, discussion of test implications with an oncologist, ductal carcinoma 0.6–1 cm Grade 2–3, HER2 negative ductal carcinomas with 1.1–4.0 cm Grade 1–2, or lobular carcinoma. This evidence concerns the gene ERBB2 and breast ductal adenocarcinoma.