You cannot process frozen samples for paraffin embedding, since that would require you to thaw the samples, making them useless for morphology. However you might still be able to work with these samples, by sectioning them on a cryostat and doing standard histologic staining. You will have to mount the tissues into blocks, using a freezing medium like OCT (ideally this would be done at the time of freezing, but can also be done later). A decent histology lab should be able to help you with the process. Hopefully the tissues have been kept in a manner that has limited drying out, which can be a problem with old tissues in freezers. Good luck.

Thank You for your answer.  Samples are stored in -80°C after being prepared for in situ hybridization, that means they have been fixed and process in specific freezing medium. I've read that it could be possible to thaw the sample in fixative and then process with standard protocol. 

Sure you can thaw the tissue in formalin and then process to paraffin. It's just that the morphology you'll get will be terrible. Freeze-thaw causes ice crystals to form in the tissue, which lead to tearing and fracturing. If you want to do histology you're much better off making frozen sections on a cryostat, which should be easy since the tissue is already in mounting medium. Then stain the sections with H&E or whatever stain you want to use. Again, best to consult a histology lab.