Novel, contrast gradient-oriented, automated chromatin texture analysis

Coarse granularity of nuclear chromatin texture is a prominent feature of most malignant cell lines. We have chosen the abrupt transition from eu to heterochromatic foci (high contrast gradient [CG]) as a novel parameter for coarseness. This feature was quantified using automated image analysis of single nuclei in smears stained by the MayGrünwaldGiemsa technique. The principle of this approach consists of eliminating, with the help of substraction between two image lowpass filters, the small grey level differences among pixels, so that only high CG values are retained on the digitized image. The sum of these distinctive microareas is then taken as a fraction of the area of the peripherally eroded nucleus, and this ratio is designated as contrast gradient index (CGI) per nucleus. This method was tested on fine needle aspirates from 11 patients with benign breast disease (BBD) and 14 with mammary carcinoma (CA). For each specimen, 60 nuclei were analyzed, with a measuring time per nucleus of about 1 min. A highly significant distinction between epithelial cell populations in BBD and CA, respectively, was obtained by variance analysis of all CGIs per nucleus (p = 2 × 10−18). The median and the mean values of CGI per specimen were the next best discriminators, followed by the modes and the standard deviation of CGI per specimen. The percentage of nuclei per specimen with CGI values of >12 was also significantly greater in CA than in BBD.