Significance of variations in section mounting technique for nuclear stereology and morphology in urinary bladder...

Owing to its toxicity it would be desirable to avoid xylene in the processing of histological tissue. Consequently, modifications of the section mounting technique excluding xylene have recently been suggested. Changes in tissue preparation might, however, influence histopathological structures used for malignancy grading of tumours. In the current study, we investigated the impact of alterations in the mounting process on the subjectively evaluated quality of nuclear morphology and on the stereologically obtained mean nuclear volume, vv(nuc), of urothelial neoplasms. Paraffin sections from 14 tumours were, after the haematoxylin-eosin staining, mounted with DPX and a coverslip either, 1) from the water bath, 2) after dehydration in ethanol but without clearing, or, 3) after dehydration and xylene clearing. We found that the nuclear morphology of ethanol-treated and xylene-cleared specimens was somewhat more brilliant than that of sections mounted from water. The vv(nuc) of xylene-cleared sections ranged from 142 to 751 microns3, and the mean value of 350 microns3 was not significantly different from that of ethanol-treated sections of 367 microns3 (2p = 0.67). In contrast, the mean vv(nuc) of sections mounted from water was 459 microns3, approximately 30% larger (2p < or = 0.02). Thus, although previous studies have demonstrated the prognostic value of vv(nuc) in patients with bladder cancer, the present study shows that modifications in section mounting technique may significantly influence the results, underscoring the need for standardization of tissue processing. Sections mounted from ethanol seem to be as good as routine xylene-cleared sections, whereas sections mounted from water have a less brilliant morphology and results of nuclear stereology different from those of routine sections.