An effective method for suspicious cases in urinary cytodiagnosis by the combined use of scanning and transmission electron microscopy following light microscopy.

In urinary cytodiagnosis, pathological characterization of atypical cells is sometimes difficult because cells in urine samples tend to be degenerated. To overcome this problem, we adopted serial examination under light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Five patients with transitional cell carcinoma primarily developed in the bladder, three patients with dysplastic cells, and one patient with metastatic and infiltrative colorectal carcinoma were subjects of the present study. Sample cells were smeared on a film slide especially suitable for serial use (a film slide used in X-ray diagnosis), fixed in 1% glutaraldehyde (GA) for 30 min, stained with Papanicolaou (Pap) staining, and immediately processed for fixation in 2% paraformal-dehyde (PA) and 2.5% GA. Slides were postfixed in 0.5% osmium tetroxide. Then, cell samples were subjected to a series of observations under LM, SEM, and TEM. One of three patients in whom dysplastic cells were suggested under LM was finally diagnosed as transitional cell carcinoma by subsequent examination under SEM followed by TEM. Thus, serial use of LM, SEM, and TEM proved useful in discriminating transitional cell carcinoma (grade 1) from dysplastic cells and also in distinguishing metastatic tumor cells from primary tumor cells in urine samples.