Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Charlie was limping and has a swollen lymph in his right back leg and a fever. Of course this would make any one concerned.
Lymphoma is one type of cancer that we have had pretty good success with controlling for a period of time with chemotherapy. His prognosis will depend upon several things. We stage lymphoma to help us determine our patient's prognosis as well as a treatment plan. That is based upon where the cancer is found, the type of lymphoma he has, blood calcium levels and how sick he is otherwise.
Small cell lymphoma has a better prognosis than large cell.
If he has one or only a few external lymph nodes affected now he has a better prognosis than if he has several external and internal lymph nodes affected and a much better prognosis than dogs that have organ (spleen or liver) and/or bone
marrow involvement too.
The sicker he is (not eating
, losing weight rapidly) the poorer his prognosis. Dogs that seem to feel great and appear normal other than having lymph node enlargement have a better prognosis.
Having said all of that dogs with lymphoma rarely have a fever with just one lymph node involved. It is possible that your fellow has an infection rather than cancer. I would recommend that he be tested for tick borne diseases too, and looking for bacteria on his aspirate.
If your veterinarian believes he does have lymphoma consulting with a veterinary oncologist will be very helpful to determine a course of action. If this is lymphoma and it is not treated he will generally have less than 3-6 months. If he is given steroid therapy alone that can improve his quality of life, but it may not extend his life much. These pups generally don't live much longer than 6 months. With aggressive chemotherapy he can have a couple years. In dogs we don't try to cure, their lives are too short to make them really sick for a possible cure, rather we treat them to extend quality life span. We try to make them feel as good as possible for as long as possible.
Please let me know if you have any further questions.