Microwave fixation and rapid processing in a large throughput histopathology laboratory

Technical details of a method of microwave fixation and rapid processing are described. Fresh biopsy specimens are sampled and trimmed into 2 mm thick blocks and irradiated to a temperature of 68 degrees C. They are then processed through cycles of absolute alcohol (75 min), xylene (50 min) and wax (50 min). It is possible, in this manner, to run several 'short' cycles of about 3 hrs each during the working day so that stained sections are available on the same day as receipt of the specimens. Endoscopic biopsies are processed through a shorter cycle comprising 30 min of absolute alcohol (4 changes), 20 min of xylene (3 changes) and 20 min of wax (2 changes). For convenience we also employ an overnight cycle whereby microwave-fixed blocks are processed through several changes of absolute alcohol, xylene and wax without the use of formalin. This method of processing not only removes the use of noxious and potentially toxic formalin but also allows rapid preparation of good quality diagnostic sections with superior antigen preservation compared to formaldehyde fixation.