Continuous-specimen-flow, high-throughput, 1-hour tissue processing. A system for rapid diagnostic tissue preparation.

Abstract

CONTEXT: Current conventional tissue-processing methods employ fixation of tissues with neutral buffered formalin, dehydration with alcohol, and clearing with xylene before paraffin impregnation. Because the time required for this procedure is usually 8 hours or longer, it is customary to process tissues in automated instruments throughout the night. Although this time-honored method continues to serve histology laboratories well, it has a number of shortcomings, such as a 1-day delay of diagnosis, the need to batch specimens, the relatively large volumes and toxicity of reagents used, and the extent of RNA degradation. OBJECTIVE: To describe a rapid new method of tissue processing using a continuous-throughput technique. Design.-We used a combination of common histologic reagents, excluding formalin and xylene, as well as microwave energy, to develop a rapid processing method. The effect of this method on the quality of histomorphology, histochemistry, immunohistochemistry, and RNA content of processed tissue was compared with that of adjacent tissue sections processed by the conventional processing technique. We also assessed the impact of this rapid processing system on our practice by comparing the turnaround times of surgical pathology reports before and after its implementation. RESULTS: The new processing method permitted preparation of paraffin blocks from fresh or prefixed tissue in about 1 hour. The procedure allowed continuous flow of specimens at 15-minute intervals. It eliminated the use of formalin and xylene in the processing and used considerably lower volumes of other chemical reagents. Histomorphologic, histochemical, and immunohistochemical results were comparable to the parallel sections prepared by the conventional method. The new technique, however, preserved higher quality RNA. Use of the new methodology led to the diagnosis and reporting of more than one third of surgical pathology specimens on the same day that they were received, as compared to 1% of same-day reporting before the implementation of the rapid processing system. CONCLUSION: The quality of hematoxylin-eosin, histochemical, and immunohistochemical tissue sections provided by the new system is comparable to that obtained following the conventional processing method. The new system preserves RNA better than the conventional method. It also shortens the processing time to about 1 hour from the receipt of fresh or prefixed tissue, eliminates the need for formalin and xylene, and reduces the volume of other chemicals. Most importantly, it impacts overall patient management by allowing for considerably shorter turnaround times for completion of surgical pathology reports.