Microwave fixation in diagnostic renal pathology.

Microwave-fixed tissues were examined in 10 patients undergoing diagnostic renal biopsy. A small portion of renal tissue was fixed by microwave irradiation and subsequently processed by routine methods for light microscopic, immunofluorescent and electron microscopic studies. The remaining portion of specimen was fixed and processed by conventional methods. In light microscopic examination, the renal architecture and cell morphology were well-preserved. Pathological changes were identical to those seen with formalin-fixed tissue. The pattern, distribution and intensity of positive immunofluorescence in microwave-fixed tissue were similar to those in tissues directly snap-frozen and stained. In electron microscopy, the normal and pathological features were well-demonstrated and not different from those observed in glutaraldehyde-fixed specimens. Specific ultrastructural lesions were clearly demonstrated and, apparently, were not altered by microwave irradiation. Our preliminary data indicate that microwave fixation can be effectively applied in the processing of renal biopsies. As the fixation is rapid, this method may be valuable in circumstances when an urgent diagnosis is required.