Since the material has been fixed in formalin the thrombin clot
method may not be appropriate unless the tissue is well rinsed with
buffer or saline prior to cell block formation.

You could melt agar (obtained from any microbiology lab) and add this
to the tissue. After gelling, process as usual, or

Add a little alcohol to the pellet, mix and then add some OCT. Mix
gently until a clot forms and continue processing from alcohol
(Arisio Diagn Cytopath 8(4):424), or

Try the Shandon cell block technique which works quite well as long
as the tissue does not come into contact with phosphate salts.


Tony Henwood
www2.one.net.au/~henwood