I seem to find from searching google and such that it depends on what you will look at by IHC. Since we are not exactly sure at the moment, I'm looking for what would be the most universal technique, methanol or formaldehyde? 

We always make a cytospin or two and use hema fixative(methanol, as I understand)  and hema stains, for a differential count. Would this hema fixative be compatible with IHC later on? 

Is long term storage of the cytospin not possible? I read from a few sources that 1 month is about the limit.

Thanks to any and all for advice/ recommendations!!!