Expression of both PAK4 and P54 in breast cancer was much higher than that in breast fibroma and increased gradually as breast cancer progressed (advanced invasive 32.6 ± 8.2 % > early invasive 12.4 ± 3.5 % > noninvasive 2.0 ± 0.5 % > breast fibroma 0.2 ± 0.1 %; F = 20.325, p < 0.001). The gene discussed is PAK4; the disease is breast carcinoma.