High-grade urothelial carcinoma with hypochromatic chromatin in urine cytology

Abstract

Some high-grade urothelial carcinomas (UCs) in urine cytology have hypochromatic chromatin, but the incidence and criteria for diagnosis are not well described. Urine cytology cases with biopsy follow up were reviewed. Cytospin preparations from 331 cases with biopsy follow up (230 benign/low-grade UC, 101 malignant) were reviewed. There were no false-positive cases. Cases with malignant cells with hypochromatic chromatin were identified in a total of 17 cases (16.8% of all malignancies). These comprised 2 carcinoma in situ, 11 high-grade papillary UC, 3 invasive UC, and 1 adenocarcinoma. Sixteen of 93 high-grade UCs (17.2%) had cells with hypochromatic chromatin. These cells were the only type of malignant cell in 4 of 101 cases (4.0%). All cases had cells with high nuclear-to-cytoplasmic ratios and markedly indented and irregular nuclear membranes that could be identified on both cytology and subsequent histology. Malignant urothelial cells in urine cytology with hypochromatic chromatin can be present in 17% of cases and can be diagnosed as "positive for malignancy" based on their high nuclear-to-cytoplasmic ratio, and markedly indented and irregular nuclear membranes.