Rat tumor detaching naturally from body

Hello, My almost 3 year old rat has developed a benign tumour (Mammary Fibroadenomas on his belly if I'm not mistaken) and I've been to the vet a few times and they told me that he doesn't have long and that the tumour can't be surgically removed because my rat probably wouldn't wake up from the anesthesia. A scab has developed on the tumour a month or two ago and in the past two weeks I've been noticing skin detaching around the tumour in random spots (vet told me it's because his skin can't stretch so much, hence that and the scab). My question: 3 days ago I noticed skin detaching once again, but it wasn't attaching back with a scab, it just continued detaching all along the sides of the tumour. Today my rat stood up for 2 seconds and I noticed that almost the whole tumour had detached from his skin (not only the sides were detached from his body, but even the interior tumour had detached, sort of like if you went and cut off the tumour but only left a bit of skin on one side attached so it's still attached to him but barely, I saw the inside of the tumour and it's white, i dont really know how his belly looks like because im scared of picking him up so as not to further detach the tumour and such). This is my first time seeing this and I really don't know what to do, should I just leave him be, take him to the vet again, try to maybe bandage the tumour so it doesn't move anymore, euthanize him if it's onoy going to get worse for him (maybe infection since he now has a huge open wound not closing etc) , or anything else? Also just a side note, he is eating and drinking normally, doesn't move much but does a bit from time to time, and is not in any visible pain (no squeaks or such). Sorry for the long explanation, I just can't seem to take a good picture of it and thought this backstory would maybe help.

Hello  It sounds as though you can see to the inside of this lump, so there must be full-thickness wounds to the skin.  At best, whatever is going on, this sounds painful.  Imagine the pain of having such a split / wound to your own skin that shows the inside (furthermore, in some situations this may have the weight of a lump hanging from it;  in others it may pull against the floor).  The skin has a high number of nerve endings within it.  Small animals do not show signs of pain very obviously:  if a small animal in pain stops and 'looks' in pain, they will immediately be identified by any predator that happens to be around, as an easy target.  Thus tiny animals may have evolved to hide their pain from larger, predatory species, but this doesn't mean that they don't feel it.  It just makes it harder for humans to recognize (we expect high pitched noises or the animal to stop eating, but more often than not, these things don't happen).  I have never heard of a tumour or lump simply falling off to leave a healthy pet behind I'm afraid, so please do not count on it happening here.  It sounds as though your small one could be in pain, prone to infection and may be suffering.  Euthanasia may indeed be appropriate;  your vet needs to assess this for you.

Hi, I wanted to thank you for the fast and informative reply. I also wanted to give you a bit of an update, because you mentioned you never heard of a tumour falling off and leaving a healthy rat behind (neither have I, so the following events left me in quite of a shock) . I went to the vet for euthanasia, they didn't want to do it since he was eating and drinking and gave me something to disinfect the wound on his belly daily. I wasn't in high hopes but I still decided to try and help him as much as I could. Today the tumour finally detached fully from his skin so I went to inspect his belly, and I was suprised that there was no visible wound anymore;he healed fully, only his fur is missing on that part of his body. He is doing well, eating and drinking normally, and I couldn't be more relieved :)  

Awesome!  Thankyou for that.  I will do some research and see if I can work out what I need to read up on.

Are you able to suggest a veterinarian that has a good reputation for me? I tried to get help from a veterinary hospital, but it was unsuccessful.

thank you!