We present a new non-invasive label-free imaging method, which visualizes tissue dynamics/sub-cellular motion by analyzing the temporal fluctuation of optical coherence tomography (OCT) signals. Our modality has been utilized for visualization and quantification of the time course necrotic process of human breast adenocarcinoma spheroid (MCF7). The response of MCF7 spheroid against anti-cancer drug has also been investigated. The presented method is quantitative. So, the necrotic process was not only shown by images but the dynamics signal value is also plotted as a function of time. It showed clear degradation of tissue activity by time.