Any one has tips on frozen sectioning fatty tissues e.g. Margins, lymph nodes? The high fat content made it very very challenging to get a good section.
secondly, If you have tips on cutting Fatty tissue post FFPE processing do share too! as FFPE margins tend to ski across the waterbath when you put the section on water..
In my experience it is very difficult to cut fat in the cryo at least for thin sections. If I really have to get any readable section I cut at 10-20 µm for margins in breast tissue for example. For lymphnodes one has to decide if you want to see either fat or lymphnode on the slide. We usually cut at 5 µm and "rescue" the non-fatty part.
Regarding your question about fatty FFPET: it helps very much to prolong the processing times in concentrted ethanols, xylen and paraffin. It depends on your protocol, size of tissue. Sometimes it may help to get better slides of fatty blocks, to let the tissue sit for an additional day (or night) in molten paraffin to get rid of residual ethanol and xylen.
I was able to make reasonably good frozen sections from epididymal and abdominal fat of rat at 10 micron thickness. I kept chamber temperature at -50 and block holding arm temperature of -18. Tissue blocks are made from frozen fat tissue in OCT using dry ice methanol slurry method. Styro foam box placed in the hood was filled with dry ice up to two inch level. Immersed a petridish in the dry ice and filled it with dry ice. Poured methanol over the dry ice slowly to fill the petridish and allowed it to cool. A rubber float (similar to the one commonly used to float the micro centrifuge tubes in the hot water bath) was suitably cut to accommodate the (Tissuetek) plastic mold. Placed the float along with the tissue mold on the slurry made above. Added the OCT into the mold and allowed to cool than placed the tissue in the cold OCT and allow it to get solidified. In this fashion keep of adding the OCT in layers till the tissue is completely covered in solidified OCT there by preventing tissue thawing. Blocks were stored at -80. Excess OCT can be trimmed with care to keep sufficient OCT around the tissue.