The present invention relates to a method and system for analyzing mechanical signatures of a plurality of cells for metastatic detection. Specifically, a data set characterized by at least one metric (such as Brillouin frequency shift and/or Brillouin linewidth) representing a cell mechanical signature is acquired for the plurality of cells by using a label-free Brillouin spectroscopy. A merit function is calculated based on one or more statistical characteristics of the data set, such as sensitivity and specificity. Then, the plurality of cells can be classified to detect metastatic cells based on mechanical signatures provided by the data set and an optimal metric value delivering maximum to the merit function.