Difficulties in evaluating urinary specimens after local mitomycin therapy of bladder cancer

In order to describe the cytological changes induced by mitomycin in urinary specimens, we re-examined cytological specimens from patients with recurring bladder cancer treated by long-term intravesical mitomycin therapy after transurethral resection. Local mitomycin therapy causes an increase of leukocytes and urothelial cells, especially of the umbrella-cell type, in urinary specimens. During and after the application of mitomycin, the nucleus and the cytoplasm of urothelial cells are enlarged, usually proportionally. Urothelial cells frequently show a giant nucleus, multiple prominent nucleoli, and an enlarged foamy cytoplasm of the umbrella-cell type. Anisokaryosis is also seen. Such cytological changes are more remarkable later in the course of therapy and after the end of therapy, and they often confuse cytological interpretation. However, the nuclei of urothelial cells are usually translucent and not hyperchromatic, and there is rarely a coarse chromatin pattern. On the other hand, in positive specimens during or after local mitomycin therapy, usually a number of tumor cells showing nuclear enlargement, hyperchromatic nuclei, coarse chromatin pattern, and/or increased nuclear-cytoplasmic ratio are found beside the atypical cells changed by mitomycin.