Biopsy Cycle Tissue Processing

Variables that affect tissue processing are tissue size (i.e., fine needle or core biopsy versus wedge versus organ resection), tissue thickness, and tissue density. These variables affect how quickly processing reagents will penetrate the tissue sample. Due to the smaller size, fine needle or core biopsy tissue requires less time for fixation and subsequent processing steps (e.g., dehydration, clearing, and paraffin infiltration) than a wedge or organ resection.

As each processing step is dependent upon the other, it is important not to compromise the diagnostic quality of the biopsy specimen by rushing any of the processing steps. Biopsies that are processed using a routine processing protocol used for large tissue may become brittle and hard due to over-processing. A separate, routine biopsy tissue processing cycle is recommended for liver biopsies to achieve consistent, high-quality results, assuring that the biopsy is neither over- nor under-processed.

Table 2 provides an example of a routine biopsy tissue processing cycle. Note that the first two steps in formalin are only one minute in duration. This is because the processor is filled with formalin and the biopsies are immersed until the processing cycle begins to assure that the program is complete at its scheduled end time, for example, 4:30 AM.