I've used HistoGel and have also used agar. As poured media become less 
common in microbiology labs, and histology labs have ever less equipment, it 
becomes difficult to prepare or borrow agar (I think I remember a 3% 
preparation). Agar embedding has many advantages; its major disadvantage for 
the pathologist is that it's extremely time consuming to do it while grossing.

Cell blocks are essential for examining pleural fluids and similar materials, 
but I can't imagine doing without a Pap stain. Jeff Silverman at Southside 
Hospital in Bay Shore NY reports >>We just decided to do all fluids as cell 
blocks and are eliminating the cytology service, except for FNA's, completely 
due to all the regs nowadays.<< This is an appalling decision in terms of 
patient care, but I think more and more small pathology services will be 
making it.

Bob Richmond
Samurai Pathologist
Knoxville TN