Xylene-free method for histological preparation: A multicentre evaluation

The backbone of daily pathological diagnostic work is the paraffin section. Paraffin sections are still prepared by methods largely unchanged for over 150 years. A xylene-free method has been developed that excludes xylene, n ot only as the intermediate step before the paraffin baths, but also for de paraffinizing of the cut sections, which also eliminates the need for rehyd ration and dehydration for the staining and mounting steps. Elimination of xylene from tissue processing cuts costs, saves time, and improves the labo ratory environment. Experience with xylene-free sections since 1995 at the Vrinnevi Hospital is favorable. Our opinion is that the xylene-free section s are equivalent to conventionally processed sections. To test this hypothe sis, nine pathologists from three hospitals participated in an evaluation t rial. Paired tissue blocks from 10 consecutively submitted samples each of breast, intestine, and skin were processed by either the xylene-free or the conventional method. Sections from each block were deparaffinized and stai ned with hematoxylin-eosin (H&E), with periodic acid-Schiff (PAS), and with van Gieson's method. A randomized mix of 180 sections (10 samples x 3 tiss ues x 3 stains x 2) gave 90 matched pairs. Each section was blindly examine d and scored by nine pathologists to give 810 paired observations for stati stical evaluation. The xylene-free sections were ranked as good as or bette r than their conventional counterparts in 74% of the comparisons, and poore r in 26%. The major discriminating factor was the staining method. H&E and PAS sections were equivalent. The xylene-free van Gieson sections, cut from the same blocks and randomly assigned to this stain, tended to be downgrad ed. This could be traced to a faulty stain solution used for this batch. Th e overall results have demonstrated professional acceptance for the xylene- free method of processing histological sections.