Preparation of frozen cell-block sections amenableto diagnostic immunocytochemistry: a technical report on cryo-embedded cell-block method

Modified agarose cell-block (CB) technique can be effectively used to have the CB embedded in the OCT compound for the preparation of frozen CB (F-CB) sections in the same way as in the preparation of frozen sections from cryoembedded fresh tissue samples for the intraoperative consultation. In this report, we demonstrate the amenability of F-CB sections to the diagnostic immunocytochemistry. The pelleted cytologic material was at first compactly embedded in ultralow-gelling temperature agarose gel and then re-embedded in conventional agarose gel. The resulting agarose-embedded cell-pellet was cut in halves so that one half is embedded in OCT compound for cryosectioning on a cryostat, while the other half is reserved for the preparation of paraffin-embedded CB (P-CB). The F-CB sections were comparable to sections cut from the paraffin-embedded CB in terms of the quality of H&E-staining and immunocytochemistry. We suppose this method can also facilitate a rapid quantitative and qualitative assessment of the future P-CB. We have extended this technique to the cryo-embedded cell-block method, in which the compact agarose cell pellet is directly embedded in the OCT compound so that the frozen sections can be cut from the cryo-embedded cell block in the same way as in intraoperative frozen section analysis. In this technical report, we illustrate how the frozen cell blocks (F-CBs) can be effectively prepared not only from liquid-based cytology samples but also from conventional fine-needle aspiration cytology slides.