1. A method for segmentation of a mass object appearing in a digital image of mammalian tissue, the digital image provided by a medical image acquisition system and the method used with a computer aided diagnosis (CAD) system, said method comprising the following steps: providing a reference object center pixel; separating the mass object from its background in the digital image by determining a segmentation contour around the reference object center pixel and calculating an object center pixel within the segmentation contour; comparing the calculated object center pixel to the reference object center pixel, and if they are deemed equivalent according to a predefined criterion, accepting the segmentation contour from which the calculated object center pixel was determined; and if the calculated and reference object center pixels are deemed to be non-equivalent, iterating said steps of providing, separating and comparing until equivalence is reached or until a predefined number of iterations is reached, which ever is first, wherein the reference object center pixel in the initial cycle of said method is a user or CAD system selected pixel, and in all said steps of iterating of said method, the reference object center pixel is the immediate previously calculated object center pixel.