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.

A method of rapid fixation of large biopsy specimens using microwave irradiation.

This report describes the use of microwave irradiation for the rapid fixation of large biopsy specimens. Two hundred and twelve fresh large specimens subjected to non-ionizing irradiation in a domestic microwave oven (600 watt output, 2450 MHz) for 4-9 min were rendered sufficiently firm to be dissected and sampled immediately without the need for any formalin fixation. The tissues hardened in this manner remained pliable, retained much of their natural colour and were free of noxious fumes. Lymph nodes became opaque and firm and their pink-tan colour contrasted with the bright yellow of adipose tissue, making them easily dissectable. This procedure, combined with a further 4-7 min exposure to microwaves of the trimmed tissue blocks (in batches of 40), completed fixation and allowed the specimens to be processed on a 3 h 15 min cycle in an autoprocessor which did not contain formalin.