The two-step vacuum-microwave method for histoprocessing.

When microwaving and vacuum is combined, decrease of boiling temperature can be exploited in the histoprocessing procedures allowing a completely novel approach for impregnating tissue with paraffin. We found that, if the pressure is sufficiently low in the paraffin step, no ethyl-alcohol step is necessary for the dehydration. In that case, the fixed tissue blocks can be directly placed into the isopropanol and, after that, in the hot paraffin, in which the final dehydration of the tissue takes place. The full histoprocessing procedure can thus be shortened into two steps only, with a processing time (for 72 biopsies) of a mere 40 min. Working completely without ethyl alcohol might be of interest for countries in which ethyl alcohol is difficult or expensive to obtain. We conclude that vacuum-microwave histoprocessing allows us to omit ethyl-alcohol dehydration and to replace xylene, resulting in a two-step 'green' (ecological) method.