A method for determining a mechanical property of a nucleus of at least one cell in a sample comprising: acquiring the at least one cell's mechanical signatures using label-free cytometry enabled by Brillouin spectroscopy, wherein the label-free cytometry comprises the steps of: illuminating the sample by a light beam (110; 210; 1210; 2110; 2628) along a first direction; collecting a Brillouin scattered light emitted from the sample in response to the illuminating light beam; sending the Brillouin scattered light to an optical arrangement to induce a spectral dispersion and to a detection unit (120; 227; 329; 723) to generate a spatio-spectral pattern (1310, 3404) of the Brillouin scattered light, wherein the optical arrangement and the detection unit (120; 227; 329; 723) are positioned along a second direction; detecting the spatio-spectral pattern (1310, 3404) of the Brillouin scattering light onto the detection unit (120; 227; 329; 723), wherein multiple points of the sample along the illuminating light beam (110; 210; 1210; 2110; 2628) are measured simultaneously; wherein at least one of the multiple points of the sample is a cell nucleus; calibrating the spectral pattern at each spatial point at the detection unit (120; 227; 329; 723); and calculating the one or more Brillouin metrics at each measured sample point based on the detected spatio-spectral pattern, wherein the one or more Brillouin metrics are selected from the group consisting of: Brillouin frequency shift, Brillouin spectrum line width, Brillouin gain or loss spectrum, and a combination thereof; wherein, calculating the one or more Brillouin metrics comprises creating a histogram from the spatio-spectral pattern, determining each peak within the histogram, wherein each peak represents mechanical signature from different regions within the cells, and identifying the peak corresponding to the at least one cell nuclei, and classifying cells based on the cells mechanical signatures of the at least one nuclei, wherein the determined mechanical signature corresponds to a physical property of the at least one nuclei, wherein the cells are classified as cancerous or non-cancerous, and wherein cancerous cells are classified as metastatic, non-metastatic or localized lesions. illuminating the sample by a light beam (110; 210; 1210; 2110; 2628) along a first direction; collecting a Brillouin scattered light emitted from the sample in response to the illuminating light beam; sending the Brillouin scattered light to an optical arrangement to induce a spectral dispersion and to a detection unit (120; 227; 329; 723) to generate a spatio-spectral pattern (1310, 3404) of the Brillouin scattered light, wherein the optical arrangement and the detection unit (120; 227; 329; 723) are positioned along a second direction; detecting the spatio-spectral pattern (1310, 3404) of the Brillouin scattering light onto the detection unit (120; 227; 329; 723), wherein multiple points of the sample along the illuminating light beam (110; 210; 1210; 2110; 2628) are measured simultaneously; wherein at least one of the multiple points of the sample is a cell nucleus; calibrating the spectral pattern at each spatial point at the detection unit (120; 227; 329; 723); and calculating the one or more Brillouin metrics at each measured sample point based on the detected spatio-spectral pattern, wherein the one or more Brillouin metrics are selected from the group consisting of: Brillouin frequency shift, Brillouin spectrum line width, Brillouin gain or loss spectrum, and a combination thereof; wherein, calculating the one or more Brillouin metrics comprises creating a histogram from the spatio-spectral pattern, determining each peak within the histogram, wherein each peak represents mechanical signature from different regions within the cells, and identifying the peak corresponding to the at least one cell nuclei, and classifying cells based on the cells mechanical signatures of the at least one nuclei, wherein the determined mechanical signature corresponds to a physical property of the at least one nuclei, wherein the cells are classified as cancerous or non-cancerous, and wherein cancerous cells are classified as metastatic, non-metastatic or localized lesions.