1. A method of histological assessment of nuclear pleomorphism by identifying image regions comprising respective groups of contiguous pixels and potentially corresponding to cell nuclei in histological image data, the method including using computer apparatus to carry out the steps of: a) thresholding the image data to render it binary with identified image regions and background distinguished from one another by association with different binary digits, b) determining perimeters and areas of identified image regions, c) calculating image region shape factors from the perimeters and areas, and d) assessing nuclear pleomorphism from the shape factors' statistical parameters.