Fourier shape features discriminate simple and complex shapes in histological renal tumor images. The bar graphs illustrate the distribution of the second harmonic’s major axis length of all the shapes in the nuclear mask for (a) a chromophobe and (d) a papillary image. (b) - (c) and (e) - (f) are original image and nuclear mask shapes of chromophobe and papillary, respectively. Cyan shapes: simple elliptical nuclei for which the 2nd harmonic major axis length, representing amount of detail, falls in the first seven bins of the histogram (cyan bars in the bar graph); Blue shapes: complex nuclear clusters for which the 2nd harmonic major axis length falls in the last seven bins of the histogram (blue bars in the bar graph). It can be observed that, due to the complex clusters of nuclei, papillary has more shapes that have high major axis lengths. Therefore, the frequency of shapes in these bins can be an informative feature for distinguishing papillary from chromophobe.