Of course, the surgery can be successful. If the tumour is not malignant and it is located in some easily operable place, for example on a fin, the surgery is easy and will be successful with a very high probability if done by a vet or even a skilled amateur. On the other hand, a malignant tumour already grown into some vitally important tissue may be inoperable. If any trace is left, it will grow again.
This is based on my 30-year experience of keeping and breeding tropical fish. If you want scientific articles, I bet there are many, but finding them might be a lot of work - here, for example, a koi healthy 15 months after a malignant tumour surgery: https://pdfs.semanticscholar.org/f1de/fb2d1effea3e64506b0e65dd8d6b28349507.pdf