1. An image processing system for digital pathology comprising a processor and a memory coupled to the processor, the memory storing a digital image of a biological tissue sample and storing computer-executable instructions that, when executed by the processor, cause the processor to perform operations for discerning a cell nucleus boundary in the digital image, said operations comprising: identifying, by the processor, one or more initial edges in the digital image and using the pixels within the identified initial edges as initial voting pixels; using, by the processor, a tensor voting field for performing tensor voting operations on pixels in a neighborhood of each of the initial voting pixels; accumulating, by the processor, a plurality of votes for each of the neighboring pixels to determine a tensor value for said neighboring pixel, the amount of the vote indicating whether said neighboring pixel is likely to be an edge pixel of the same nucleus as the initial voting pixel, the tensor value being a sum of all votes cast by all initial voting pixels in whose neighborhood said neighboring pixel lies; decomposing, by the processor, each of the determined tensor values for determining eigenvalues and eigenvectors of the decomposed tensor value; evaluating, by the processor, the determined eigenvalues and eigenvectors for identifying refined edge pixels, the refined edge pixels representing the cell nucleus boundary; and generating, by the processor, a saliency edge strength image which selectively comprises the identified refined edge pixels representing the cell nucleus boundary.