I went into work because I didn't really know what else to do with myself! In hindsight it was probably the right decision for me because I had to wait 6 weeks for my surgery so I would have been off work for ages otherwise. I would have only been at home worrying and an emotional wreck if I wasn't at work.
That said my colleagues didn't expect much from me and I was very lucky at how supportive they all were :) My closest friend at work sat for hours with me while I was a gibbering wreck... I'll never forget her kindness.
I used the time to hand over all my work, routine tasks, share knowledge etc so that it would all be handled while I was away and I didn't worry about any of it while I was off. And that was very reassuring.
Ironically work were great when I was diagnosed but piled on the pressure when I went back and was 'better'. Within a year I had left and found a less well paid but less stressful and more rewarding job analysing data for the NHS.
So do what feels right for you. Remember if you decide to go in and you can't hack it, you don't have to stay!!! Also, this illness may change what you want from life so don't work because you feel you should!