An improved method for sequential light and scanning electron microscopy of the same cell using localising microcoverslips.

Cytologic material may contain cell clusters and tissue debris, which are often missed on smears. The processing in parallel of both cytologic smears and sediment when available has been recommended ,1-5 for tissue fragments present in the latter increase diagnostic precision. Paraffin embedding of the sediment for histological examination presents obvious technical difficultiesandit has been proposed that entrapping cytologic material in agar4 6 or in plasma-thrombin23 makes the sediment compact and easier to handle. We have devised a technique in which the sediment is folded in a celloidin film which, being permeable but insoluble in water, alcohol, and xylene, keeps the sediment compact during the process of paraffin-embedding. This method bears some resemblance to that proposed in 1936 by Wihman7 who employed a sausage-skin to collect and process the sediment of exudates and transudates. Such a procedure, however, has been neglected in recent times. Material and methods Celloidin (Chroma Ges, Stuttgart) flocks were soaked in absolute alcohol and then dissolved in ether to obtain a 10% solution in absolute alcohol-ether (1:1) which was kept in a well stoppered jar at room temperature. Neocolloidine, commercially available in solution ("Neocolidine", BDH) gave less satisfactory results being more soluble in alcohol. The cytologic material (serous fluids; washings, brushings and needle aspirates arriving at the laboratory suspended in saline) were quickly centrifuged and routine smears prepared. The sediment was then suspended in fixative (usually 95% alcohol or 10O% formalin) for histological processing. Celloidin bags ("cell-bags") were prepared (Fig. 1) by pouring the celloidin solution to the top of polypropylene plastic centrifuge tubes. The celloidin was then recovered and the tubes left upside down for a short time. A thin film of celloidin about 20-50 vm thick remained over the inner surface of the tubes,