Our techs and pathologists love the nylon mesh bags.  They are easy
to get into and, unlike Histoscreen cassettes, can be opened and layed
out flat for scraping up very fragmented specimens. We have found
several innovative uses for them including:  
1. We NBF fix our EDTA bone marrow aspirate then filter through the
bags leaving only the spicules in one corner for embedding.  Makes for
pretty immunos when using DAB. Few RBCs to deal with. 
2. We have a plastic surgeon who delights in sending the smallest skin
margins for frozen sections.  To maintain the exact orientation for
paraffin embedding, we will place one blue pad in the bottom of the
cassette, tear open a mesh bag flat, place one side of the mesh on the
blue pad and place the frozen block on top of the mesh.  Once the
block is melted off, the other side of the mesh bag is allowed to fold
over the tissue then the lid is snapped in place.  The mesh will lap over
the outside of the cassette but it doesn't make a difference.  The techs
(and Pathologists) love the way that the tissue is held orientation
identical to the frozen slides without being sucked into and stuck onto
blue pads. They say it makes embedding much easier.
3. Can be used as a substitute for large tissue processing cassettes.
Place the large tissue sample in a large mesh bag. Place the open end
of the bag just accross the open end of a labeled cassette.  Snap the
lid closed on the end of the bag.  It will hold fast during processing and
by having the bag with tissue suspended from the cassette, you get
much better fluid exchange then in any large processing cassette
we've tried.
As you can tell, I'm a big fan. I am currently writing an article on these
and many other uses we've found for those bags. I've even used one
to repair a hole in my mesh pool cover.  I know that's not histo related,
but hey... 
Terri Braud, HT(ASCP)
Anatomic Pathology Supervisor
CHRISTUS St Frances Cabrini Hospital
3330 Masonic Dr.
Alexandria, LA  71360
tlbraud@sfc.sch.org