In summary, the IKWG does acknowledge that Ki-67 has clinical validity for the determination of prognosis in patients with ER-positive early stage breast cancer [2]; however, the IKWG only supports a limited clinical utility for Ki-67 in the clinical management of ER-positive breast cancer patients, and only if an analytically validated assay and scoring system is used. The gene discussed is MKI67; the disease is breast cancer.