Hi. I was at the vet today and was told that my guinea pig has a tumour. The vet seemed to be keeping a lot to themselves because I was upset but I think they said it was in her urinary gland or something like that. She has to go back on Monday so they can remove it. I'm just really really worried she won't survive the surgery. She's young, she's only 2 and the vet said she was a strong girl but I'm really attached to her. She's my best friend and I don't know how I'd live without her. Do you have any suggestions on how to cope if the worst does happen? Or even what to do until Monday? Thank you.
I am very sorry - these are the kind of news none of us wants to hear and they always hit you right in the gut.
However, please do not panic!
Firstly - the majority of guinea pig operations are successful. By far not every tumour is malign, and even those can be got out without problems as long as they are still encapsulated. Whatever your initial reaction is, it is not necessarily a death sentence.

And as your vet did point out rightly - your girl is otherwise healthy and at the peak of her life, so she has got that in her favour to help her through the op and recovery.
The problem is - IF the tumour is malign, then letting it sit and spread would be a surefire long term death sentence. It is one of those situations where you are between a rock and a hard place, and you have to make the leap of faith for the sake of your beloved piggy.
There is no urinary gland. Could you please confirm with the clinic where the tumor is sitting? Is an external or an internal gland; do you remember that?
Here are our post-op care tips. You may want to read through them, so you are prepared. Make sure that you have got support care stuff at home so you can step in if necessary - which it hopefully won't be! That can make a real difference if things are not going quite smoothly.
Tips For Post-operative Care
Complete Syringe Feeding Guide
Administering Medications
Unless there is a sudden deterioration (loss of appetite, lethargy or the lump blowing up), then just keep her as normal as possible if she is still eating/pooing and behaving normally.
I would however recommend to switching to weighing once daily at the same time in the feeding cycle. Just before you give dinner is a good time, for instance. The daily weight variance can be up to 30g. You only need to be concerned if there is a larger weight loss from one day to another or if she is continually losing a little bit more weight with every day. In that case, you may want to start topping her up with syringe feed and water, and also contact vet clinic.