MKI67 and breast cancer: Here, we report on the Rhein-Main-Registry (REMAR) prospective, real-world German study focusing on patients with Ki-67 in the intermediate range (10–40%, as determined locally) and evaluated the reliability of this Ki-67 range as a marker to identify intermediate- or high-risk pN0-1 breast cancer patients who are likely to benefit from the prognostic/predictive information gained by the RS result.