Partner with pituitary tumor

My partner was told yesterday that he has a pituitary tumor after over 18 months of eye tests etc. He told me this morning via text about the outcome of the appointment - we don't yet live together - so we will have a conversation this evening about what treatment is being proposed.

I've read that this is unlikely to be cancerous which is comforting, but the news has shocked me, understandably. 

I want to support him and know that he'll be going through a version of hell right now, so will likely be angry, upset, emotional, in other words, human. How do I support him and keep calm about it all? 

Thanks