Lymphoma, tapeworm, both?

My dog was recently diagnosed with lymphoma which was confirmed by a pathologist. I didn't want to believe the diagnose, so I was looking for any other answers and I noticed that when he passed a stool today, there were numerous tapeworm segments on it moving about. So, my questions is, would this most likely just be a secondary issue, or is it within the realm of possibility that a tapeworm infection could lead to a false positive on the biopsy test that showed lymphoma? I tried searching the web, and while most sites indicate that dogs with tapeworm infections rarely show major symptoms, some suggested that complications can arise.

Hello!  It sounds as though your dog has been very unlucky and had lymphoma diagnosed, from a biopsy.  You could ask your vet how certain they are about the diagnosis, but presumably if they have come to you with this diagnosis, they will be confident.  Lymphoma can cause signs such as diarrhoea and weight-loss, although that depends how early it is caught;  I have even diagnosed lymphoma in dogs whose only clinical sign was a very large lymph node that I found during a routine examination. Animals with lymphoma can have low immunity (they have excessive immune cells but cancerous immune cells don't always get the job done).  This can make them more likely to prevent with minor illnesses such as worms.  We call this a secondary effect.  It is true that worms can also cause intermittent diarrhoea, but I trust that the diagnosis you were given was not only because of the diarrhoea (there are many, many causes of diarrhoea), but from pathology tests.  In real life in developed countries, worms only very rarely cause weight-loss in fully grown, healthy animals.  I would expect the lymph node microscope pathology in diarrhoea caused by worms to be different from the histology in a lymphoma case. However, I don't know the details of your dogs' presentation and I am not your vet.  Lymphoma is understandably a hard diagnosis for owners to take in so your vet will not be surprised if you call back with more questions.  There is a site called the RALPH site for owners of pets who are facing unexpected illness or grief;  they are also a brilliant resource. One of my colleagues has written a blog that includes lymphoma in dogs:  https://vethelpdirect.com/vetblog/2021/04/12/why-are-my-dogs-lymph-nodes-enlarged/ Best of luck.

Hello again - that was a huge splurge of information, so my apologies for that.  Specifically to answer your questions:  1) I have never heard of worms causing a false- positive test for lymphoma, but your vet and pathologist are the best people to confirm that as they know what tests they have done.  2) Worms rarely do show symptoms in fit, healthy dogs.  3) Lymphoma is effectively a cancerous immue system.  Reduced immunity can cause a dog pick up worms on top of an existing condition.  4)  There is an address above for the Ralph site and a link to a general article about lymphoma, which can understandably  come as a shocking diagnosis in a dog.

Finally, I would like to wish you and your dog all the best after what is obviously an upsetting diagnosis, whichever route you chose to go down next.