MKI67 and neoplasm: For HER2+ tumours, we found that incidence rates of tumours with Ki-67 ≥ 15% increased from 11.4/100000 person-years among women born before 1929 to 17.2/100000 person-years among women born in 1929 or later (HR 1.6, 95% CI 1.1–2.4).