Dog has 4 swollen lymph nodes. Is this most likely lymphoma?

I took my 6yo golden retriever, otherwise healthy, to the vet today after a week of lethargy and little appetite and she immediately noted 4 swollen lymph nodes, both submandibular and both popliteal. They are doing a CBC and fine needle aspirate but of course I am spiraling on Dr google. This is really most likely to be lymphoma, right? And must be progressing somewhat quickly?

• Species: canine

• Age: 6 years

• Sex/Neuter status: spayed

• Breed: golden retriever

• Body weight: 175

• History: n/a

• Clinical signs: lethargy, loss of appetite, swollen lymph nodes

• Duration: 8 days

• Your general location: CA

• Links to any test results, X-rays, vet reports etc. that you have: n/a