In a multivariable Cox proportional hazards regression analysis the presence of ITCs was an independent prognostic factor for breast cancer-specific survival (HR 4.13, 95% CI 1.75–9.77; P = 0.001) together with Ki-67 proliferation index (HR 2.93, 95% CI 1.86–4.60; P < 0.001). Here, MKI67 is linked to breast cancer.