Antigen preservation in microwave-irradiated tissues: a comparison with formaldehyde fixation

A wide range of immunoreactive antigens commonly investigated in diagnostic pathology were evaluated in tissues subjected to fixation by microwave irradiation in normal saline to 63 degrees C. All of the 23 antigens studied were well preserved and compared with corresponding tissues conventionally fixed by formaldehyde for periods of 16 and 18 h, respectively, immunostaining in microwave-irradiated tissues was clearly superior, being more intense and also more extensive. Proteolytic digestion was not necessary for irradiated tissues except for the staining of cytokeratins and desmin. It was also possible to stain for Leu-14 (CD22) and Leu-1 (CD5), whereas these lymphocyte antigens were lost during formaldehyde fixation. Cytomorphological details were well preserved in the rapidly-fixed irradiated tissues.