Cell Block Fixation and Processing

After preparing the cell block by any of the methods previously described, it can be fixed in either 95% ethyl alcohol or in neutral buffered formalin, according to personal preference. Use of alcohol for fixation will produce cellular morphology similar to that of alcohol fixed cytology slides, while use of formalin for fixation will give the cellular morphology more typical of tissue specimens.

If a specimen contains significant numbers of red blood cells (RBCs), they can out populate and obscure the diagnostic cells present. The offending RBCs can be eliminated (or reduced in number) by fixing the cell block in Clarke's fixative* or in any of the aldehyde formalin substitutes (such as Prefer by Anatech and Glyo-Fixx by Thermo). After fixation by either of these reagents the cell block can be processed on a tissue processor using standard formalin protocols. 

Following this, they will be embedded and sectioned like a routine tissue specimen. The number of slides prepared is determined by personal preference, although most labs require only one or two sectioned H & E stained slides.

*Clarke's Fixative:  300 ml absolute alcohol and 100 ml glacial acetic acid.