If the tumor is gone, why are the lymph nodes still enlarged?

My father has Stage 3 esophageal cancer and finished his 6 weeks of chemo & radiation. Tests show that the tumors are gone but his lymph nodes are still enlarged. What does that mean?

One of the treatments of esophageal cancer includes chemoradiation (CRT). Depending on the location and the involvement of the lymph nodes, surgery may or may not be feasible. Regardless, definitive CRT can be helpful to downstage the disease, meaning, reduce the stage of the cancer. Immediately after this therapy, there may still be lymph node enlargement because it takes time for the cancer cells to resolve. Even if all the cancer is gone, there may still be lymph node enlargement because of scarring in the tissue. About 6-8 weeks minimal is required after therapy to assess the response, and after that, if surgery is possible, then an esophagectomy can help remove the tumor/lymph nodes to see if there is residual cancer.

lymphoma. that's all I could think of. I'm not a doctor just premed.

Should they not have removed the lymph nodes? the lymph nodes are what catches the cancer, and still may have cancer cells in them, which my spread again, i would go and get advice from a cancer specialist, it can do no harm to speak to someone

If he has had chemo and radiation on eosophagus I am guessing he has a bad crop of mouth ulcers?

Our lymphatic system normally fights infection, if it is workling overtime to ight mouth ulcers or simillar, then I would expect the glands and nodes to be enlarged.

It means his body is fighting to recover.