Morphometry of nucleoli as an indicator for grade of malignancy of bladder tumors

To establish a new indicator for the classification of human urinary bladder cancers, the nucleoli of normal epithelial and neoplastic cells were analyzed, using morphometric techniques. By electron microscopy, the nucleolar profiles of cells from grade 2 and 3 transitional cell carcinomas were often small and irregular. Morphometry showed that the nucleolar volumes, nucleolar/nuclear volume ratios, volume densities of various nucleolar components, and the numbers of fibrillar centers (FCs) altered significantly with an increase in tumor grade. In particular, an increase in FC numbers in the nuclei of higher grade tumors was associated with a decrease in individual volume. The number of FCs in intact urothelial cells obtained from patients with bladder tumors is significantly larger than in the normal urothelial cells. This may be related to the multicentric origin of bladder cancers. These results suggest that morphometric analysis of nucleoli is useful in evaluating the degree of differentiation and invasive capacity of human bladder tumor cells. In particular, the number and individual volume of FCs may be an indicator of tumor malignancy.