Subvisual changes in chromatin organization state are detected by karyometry in the histologically normal urothelium in patients with synchronous papillary carcinoma

This study analyzed the chromatin organization state in histologically normal urothelium in patients with synchronous papillary carcinoma using digital texture analysis. The quantitative evaluation was carried out on hematoxylin and eosin-stained sections from 17 cases of urothelial papillary carcinoma in which a simultaneous biopsy specimen featuring histologically normal urothelium was available. Five bladder biopsy specimens of histologically normal urothelium from patients with prostate pathology in whom cystoscopy revealed a normal bladder mucosa were also analyzed. Karyometry showed that the 17 cases of papillary carcinoma, morphologically classified according to the 1973 World Health Organization scheme, belonged to a continuous spectrum or trend curve spanning grade 1 to grade 3. An abnormal pattern and distribution of the nuclear chromatin was seen in the normal-looking urothelium from the 17 bladders with papillary lesions. When this population was plotted along the trend curve, it occupied an intermediate position between the normal samples and samples from grade 1 carcinoma. When the nuclei were considered individually, the changes were detected only in a subpopulation of nuclei with chromatin alteration pointing toward that seen in grade 1 cases, even though distinct from them. In conclusion, karyometry can detect an abnormal chromatin pattern and distribution in the normal-looking urothelium adjacent to papillary carcinoma. Such alterations correspond to the so-called “malignancy-associated change.”