A system for detecting tumoral masses in an unknown tissue, that can be coupled to an MRI system for receiving a number of unknown tissue scans, each scan comprising a corresponding plurality of MRI images (Fi) relating to a set of voxels, each voxel being associated with a corresponding portion of the unknown tissue, the MRI images of each scan being indicative of values of at least a corresponding initial parameter; said detection system comprising: - first processing means configured to determine, for each voxel, a number of corresponding values of first main parameters (P p '), based on the MRI imaging; - first classification means configured to determine, for each voxel, a corresponding probability value, based on the corresponding values of the first main parameters, said probability value being indicative of the probability that the corresponding portion of unknown tissue includes a corresponding tumoral portion; - second processing means configured to select voxel groups (R 3D,1) based on: - the probability values of the voxels, a probability threshold and a geometric criterion, so that each voxel group is formed by adjacent voxels, the probability values of which individually satisfy a predetermined relationship with the probability threshold, each voxel group also satisfying said geometric criterion; or - the probability values of the voxels and a proximity criterion, so that each voxel group is formed by voxels adjacent to a corresponding relative or absolute probability maximum and satisfies said proximity criterion; - third processing means configured to determine, for each voxel group, a plurality of corresponding values of second main parameters (P r T '), each of said values of second main parameters being a function of the values of a corresponding initial parameter of the voxels of the group; and - second classification means configured to determine, for each voxel group, a corresponding aggressiveness value of the group, based on the corresponding values of the second main parameters, said aggressiveness value of the group being indicative of the aggressiveness of the tumoral mass formed by the tumoral portions present in the corresponding portions of unknown tissue. - first processing means configured to determine, for each voxel, a number of corresponding values of first main parameters (P p '), based on the MRI imaging; - first classification means configured to determine, for each voxel, a corresponding probability value, based on the corresponding values of the first main parameters, said probability value being indicative of the probability that the corresponding portion of unknown tissue includes a corresponding tumoral portion; - second processing means configured to select voxel groups (R 3D,1) based on: - the probability values of the voxels, a probability threshold and a geometric criterion, so that each voxel group is formed by adjacent voxels, the probability values of which individually satisfy a predetermined relationship with the probability threshold, each voxel group also satisfying said geometric criterion; or - the probability values of the voxels and a proximity criterion, so that each voxel group is formed by voxels adjacent to a corresponding relative or absolute probability maximum and satisfies said proximity criterion; - third processing means configured to determine, for each voxel group, a plurality of corresponding values of second main parameters (P r T '), each of said values of second main parameters being a function of the values of a corresponding initial parameter of the voxels of the group; and - second classification means configured to determine, for each voxel group, a corresponding aggressiveness value of the group, based on the corresponding values of the second main parameters, said aggressiveness value of the group being indicative of the aggressiveness of the tumoral mass formed by the tumoral portions present in the corresponding portions of unknown tissue.