Historically, the majority of tissue processing in histopathology has taken place overnight, limiting workflow flexibility. Now, the incorporation of ultrasonic technology promises to cut processing times significantly, as Neil Catlett explains.
The method of processing tissue for histological examination has remained largely unchanged for many years. Tissue processing introduces an enforced ‘delay’ in the specimen pathway during which little can be done to the specimen to speed diagnosis. Attempts have been made to improve the process (eg microwave assisted, xylene-free processors) or develop a more open system (eg continuous flow, multi-retort processors) but to date these techniques have introduced changes elsewhere in the specimen pathway, requiring redesign of either the cut-up techniques or alteration to subsequent methodologies in areas such as immunohistochemistry.
Ultrasonic vibration
The Jokoh Histra-QS ultrarapid tissue processor, available from Launch Diagnostics and evaluated in the present study, is recognisable to most biomedical scientists in histopathology as it both looks and acts like a conventional tissue processor. However, specimens up to 200 mm2 (10x2x2 mm or 5x4x2 mm) can be processed within one hour without prior formalin fixation. The processor uses xylene, graded alcohols and wax, which are pumped sequentially into a retort chamber. This chamber is then subjected to periods of ultrasonic vibration during the course of the processing cycle. Processing runs can be varied from 38 minutes upwards, depending on tissue size. Over a 12-month period, this study found the most effective cycle to be 58 minutes, which allowed a full load (20 cassettes) of mixed tissue types and sizes to be processed.
This rapidly processed tissue does not require specialised dissection techniques and from trials appears to have no detrimental effect on any subsequent laboratory techniques. Indeed, some studies have shown that preservation of certain tissue elements (eg RNA) may even be enhanced using this technique. The similarity with conventional processors means that little or no additional training is required to operate the processor (using a simple touchscreen) and also maintain reagents (the requirement for fluid exchange as with conventional tissue processors).
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