Human urinary cytology using a "direct mapping" technique: a combined light and scanning electron microscopic investigation.

A total of 252 bladder-washing and voided specimens from normal, and inflammatory and malignant lesions were examined by a direct mapping technique, i.e., a combined use of light (LM) and scanning electron microscopy (SEM). A newly-designed mesh, which consists of a piece of gelatine-covered, osmium-impregnated and polylysine-coated glass-slip with 42 compartments/25 mm2, was used in this study. This mesh permitted us to directly correlate LM and SEM images, which resulted in a shortening of the observation time. Malignancy of exfoliated urothelial cells has been determined on the basis of the presence or absence of pleomorphic microvilli as observed by SEM. Subsequently, a new "SEM grading" system for human urinary cytology was proposed. The direct mapping technique has enhanced the accuracy of the diagnosis over conventional methods, especially in cases of noninvasive, low-grade malignant tumors of the urinary bladder.