That sounds like incomplete dehydration.  A small amount of water remains in the tissue.  This prevents full infiltration by both the clearling agent and the paraffin.  Once the block is faced off, the water and/or solvent evaporates from the tissue, causing it to shrink and pull away from the paraffin.

> ----------
> From: 	histonet-bounces@lists.utsouthwestern.edu on behalf of Price, Tiffany
> Sent: 	Monday, August 4, 2008 9:56 AM
> To: 	histonet@lists.utsouthwestern.edu
> Subject: 	[Histonet] tissue falling out of paraffin block
> 
> Can anyone tell me what would make liver tissue fall out of a paraffin
> block after routine processing? We cut a routine H&E slide, and later,
> had to cut IHC stains that were ordered. The tissue was fine for the
> H&E, but the whole tissue fell out of the block when we tried to re-cut
> it, even after re-embedding. 
>  
> Thanks for any help
> Tiffany
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