Previous research has found the feeling of lymph nodes on examination can be an inaccurate assessment for cancer spread as they can be normal in size and still contain tumor cells. (vetmed.ucdavis.edu)
Another potential lymph system problem: leukemia and lymphoma can develop there. (health.com)
They usually have cancer in lymph nodes or organs, which we wouldn't have any idea of from just a blood panel. (whole-dog-journal.com)