In our study, Ki-67 showed lowest proliferative index in fibroadenomas (median 2.0%, mean 2.5%, range 1 to 10%), followed by low-grade phyllodes tumor (median 6.0%, mean 7.7%, range 2 to 30%), with high-grade phyllodes tumor showing the highest proliferation index (median 50.0%, mean 45.0%, range 20 to 70%). The gene discussed is MKI67; the disease is phyllodes tumor.