My only addition is that with the 'over-grooming' on the abdomen, I would look more towards possible skin irritations, as my uneducated (in terms of formal vet training) but long time cat person, is that if there isn't anything other than the hairballs in terms of 'vomiting' you might be more at a skin issue rather than internal. It might even have been a past issue that has resolved itself, but Obi is now in the habit of excessively grooming that area and is finding it hard to break.
It is never an easy decision, but as I say in the absence of other symptoms I would adopt a watch and see approach and save the stressful procedures when their are many pointers and definitive results from them.
Maybe talk to your vet and get a specific definition from him or her on what they would consider the difference between vomiting, regurgitation, and expelling hairballs. Like many things we might use the terms interchangeably, but they do have specific medical definitions. That might help you decide if there is really a sign of lymphoma or not, because if what is happening doesn't truly qualify as vomiting then it might not even be a consideration.
I wish you the best.
It is never an easy decision, but as I say in the absence of other symptoms I would adopt a watch and see approach and save the stressful procedures when their are many pointers and definitive results from them.
Maybe talk to your vet and get a specific definition from him or her on what they would consider the difference between vomiting, regurgitation, and expelling hairballs. Like many things we might use the terms interchangeably, but they do have specific medical definitions. That might help you decide if there is really a sign of lymphoma or not, because if what is happening doesn't truly qualify as vomiting then it might not even be a consideration.
I wish you the best.