[Histonet] Long term storage for IHC?

[Mikael Niku]

Dear Histonetters,

what do you think is the best way to store formalin-fixed tissues for 
immunohistochemistry, long-term (several years)?

We are currently fixing overnight, then rinsing in buffer and storing in 
70% or 100% ethanol, +4C or -20C. However, I don't really KNOW what 
happens here and how the tissues will work after the years. I guess 
basically the formalin fixation will be at least somewhat reversed and 
after some time the tissues will be more like ethanol fixed. But are 
there better options? Long term storage in formalin will make IHC 
difficult. And this is about large numbers of tissue samples, only some 
of which will be actually used later, so we wouldn't like to process all 
of them to paraffin either.

With best regards,
Mikael Niku
University of Helsinki, Finland