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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

When Infection Looks Like Cancer

Updated: May 15th, 2024

Many times cancer can be misdiagnosed as infection in dogs.

How does this happen?  Cancer diagnosis is not as strait forward as it may seem.

The reason for this is that we do not always have a simple test for internal cancers.  The standard of care in testing for cancer is a biopsy.  To get a biopsy, we have to be able to reach the affected area obtain a specimen.

But what about blood or urine tests?  Unfortunately, there is no easy blood or urine test that gives us a clear cut answer in diagnosing cancer definitively, although there are some companies making headway.

Here’s why cancer can look like an infection:  commonly the effects of cancer on urine or blood tests, or possibly even X-ray findings are essentially the same as an infection.  This is not to say the effects on a loved dog’s body are the same as an infection.  But, the test result or X-ray findings can look very similar.

To make matters worse, many times the cancer can house a secondary infection.  In these cases, there is, in actuality, an infection in the body, but a cancer is the real, deeper culprit.  This is a common occurrence with cancers of the nasal sinus, bladder, skin, and airways in the lungs.

When tested,  infection could be found when there is an underlying cancer.  The cancer disrupts the surface of the tumor such that bacteria can grow, and infection results.

Finally, it is important to note that systemic cancers cause immune suppression.  This lowered immune status can make the body more susceptible to infection overall, confusing test results.

In these cases, immune stabilizing supplements can help, in addition to proper use of antibiotics, surgery as appropriate, apoptogens, pain control,  and the rest of the cancer fighting tools in the Guide.


Dr D



Leave a Comment

  1. Ann-Marie Devlin on October 27, 2012 at 4:59 am

    Hello Dr Dressler

    I hope you don’t mind me contacting you, but our little 13 year old staffie, Rosie, was recently diagnosed with mammary gland cancer, (needle aspirate), together with inflammation of the pancreas (poss cancer – no definitive diagnosis undertaken – ultrasound scan only) She also has vulval beeding with undiagnosed cause, possibly benign polyps, not confirmed as vet thought her other problems outweighed further investigation. As we still felt Rosie had a lot of life in her, and not wanting to consider the only option that seemed to be open to us, we brought her home with a supply of Tramadol.

    Anyway, I came across your site when looking for advice on alternatives to help our little girl and I have been giving her Apocaps daily and follow the suggested cancer diet, mostly chicken/turkey and green vegetables. (I also give her IP6 and flax oil & cottage cheese – 1.5 tbsp to 3 tbsp). However, just before I received the Apocaps I had started to give her curcumin in the form of 2 caps of CuraMed daily and I wanted to ask you if they can be given alongside the Apocaps since they also contain curcumin. I want to give her every chance but I also am concerned about the possibility of overdosing her.

    I would welcome any comments that you have.


  2. LisaT on March 7, 2012 at 2:30 pm

    I know this is an okd question, but to Sharon asking about the VDI-TK test, we are seeing values all over the place on the forum where a number of dogs are enrolled in a study. It might be useful in a dog known to have cancer, to monitor treatment, but, as a predictor, I think it has a long way to go.

    Regarding the infection topic, we have seen a number of dogs with histories of tick diseases subsequently develop some of these cancers. Blood infections leading to blood cancers…murky waters…

  3. Jana on July 29, 2011 at 6:29 am

    Dr. Dressler,

    Thanks so much for your advice. I called my doctor and they decided to make an incision and drain the area. They sent this all off to a pathologist and I’m thrilled to say the results were completely normal. We have a followup appointment on Monday and I think I am still going to request that it be removed surgically. I don’t want it left if there is any chance of a problem in the future. My booy is the most beautiful black and silver Miniature Schnauzer most people have ever seen, with the temperament of an angel. I don’t want to take any chances with this dog. He is like my right arm!


  4. Ros on July 23, 2011 at 9:28 pm

    Dear Readers and dog lovers
    Our beautiful miniature poodle had a 6.5cm growth on his spleen removed recently, the ‘mass’ had ruptured, however he is doing very well.

    Pathologists were sent the spleen and mass for biopsy. It is approaching 5 weeks on and we do not have a clear diagnosis!! First test came back as ‘suggestive’ of lymphoma with 95% of confidence. Second test ‘stain’ came back as IF it is indeed a lymphoma it would certainly be a B-cell L. Third test PCR was sent overseas to Michigan and came back as ‘most consistent with atypical lymphoid hyperplasia rather than B cell L, 75% of confidence!?

    Hellllllllp!!!!!!! We are giving him 1000mg vit c daily, wheatgrass and flax oil/cottage cheese once daily along with a high protein low carb diet…

    Any suggestions of why we can not get a clear picture? He has now been referred to an oncologist…

    Best wishes,
    Ros xx

  5. Jana on July 18, 2011 at 6:55 pm

    Dr. Dressler,

    My beautiful, three year old, male, Miniature Schnauzer, has had what we have thought to be a subaceous cyct for more than a year. It has remained unchanged for more than a year, until now and my vet has not been concerned.

    However, I was away this weekend and the dogs were home with my husband. I came home last night and found that this cyst was almost twice the size that it was several days ago.

    I took him into my vet today and they did a fine needle aspiration. It showed puss in the blood that she removed, so it would seem infected. However, she also saw some cells that she said she didn’t recognize. She said they were probably inflamation, but recommened we remove it to be sure. She put him on 75mg Clindamycin twice a day for 14 days, and then will remove it.

    I lost both my parents within a week, two months ago. I can’t imagine waiting two weeks to find out if this spot on my constant companion is cancerous or just a cyst. Would asking for this sample to be sent to a pathologist give me more information, or should I be concerned?

    Any information would be appreciated. This dog is very, very special to me.

    • DemianDressler on July 20, 2011 at 2:30 pm

      Dear Jana,
      I am so sorry you are going through all this.
      My best advise is to contact your vet to see if he/she would be willing to do the removal surgery a little sooner. There are some advantages in using the antibiotics first (it will improve the pathologists ability to read the submitted specimen for cancer cells). Definitely get the biopsy done to be on the safe side.
      I hope this helps

  6. Dagmar on July 13, 2011 at 5:08 pm

    Thanks Dr Dressler,

    Julie was just too weak to do a bronchial wash, unfortunately she went downhills rapidly and we had to send her to doggy heaven last Saturday.


    • DemianDressler on July 20, 2011 at 3:07 pm

      Dear Dagmar,
      I am so sorry. Thinking of you in this sad time of departure.
      All my best,

  7. Anthea Reilly on July 7, 2011 at 11:25 am

    Dear Dr. Dressler,
    Many thanks for your helpful reply. I have spoken to the oncology doctor who suggested that I discontinue the Piroxicam for about a week. Bea’s blood work is excellent. The local vet examined her anal area today and, wonder of wonders, the tumor has shrunk. He did a full chest X-Ray which also shows that things are clear. I started to reduce the Apocaps a while back and, after giving her a week’s rest, I shall introduce a low dose and see how well she tolerates it. Up until recently, she has done very well and has tolerated both medications with little trouble.

    Thank you……………Anthea

  8. Dagmar on July 6, 2011 at 2:20 pm

    My dog Julie was going downhills rapidly (weight loss, loss of energy, just appearing very sick and coughing now and then). X-rays revealed a massive infection in her lung and probably tumours hiding under the infection.
    We are at the moment fighting the infection with high doses of 2 antibiotics, but I learned the antibiotics probably do not have a huge effect on lung tissue.
    Is there anything else we can do to get that infection under control?

    • DemianDressler on July 13, 2011 at 10:33 am

      Dear Dagmar,
      I would suggest a culture and sensitivity of a bronchial wash to be certain the proper antibiotic is being used. Hopefully you have read the Guide and know about proper use of immune stimulants (beta glucans, modified citrus pectin, etc). You can search this blog as well using the search bar on the upper right. And finally, it may be that if there are tumors there we need to institute cancer care- surgery if possible, chemo, apoptogens, immune stimulants, the Dog Cancer Diet, and deliberate steps to improve life quality, increase sleep in total darkness, etc.
      Dr D

  9. Anthea Reilly on July 6, 2011 at 9:57 am

    A few months ago I spoke to you on one of your web-in-ars. You were helpful. My chow/retriever mix has lived for 7 months since her melanoma tumor in the right anal sac area was removed, even though the tumor grew back. She has been on Apocaps since January. An oncologist I took her to suggested she start with Piroxicam, which I began to give her round about March. Since then, I have read that one should not give a dog Piroxicam and Apocaps together. What are your views? Bea has begun to throw up at times and a week ago she had some kind of seizure or stroke. Took her to the emergency pet hospital where they gave her a shot of Cerenia which helped to restore her balance and lack of co-ordination in the rear limbs. She has made a good recovery.

    • DemianDressler on July 6, 2011 at 2:00 pm

      Dear Anthea,
      the vet or oncologist should monitor concurrent use, but I have used a reduced dose of Apocaps at about 1/4 of the labeled dose. However, not all dogs will tolerate the combo, or piroxicam at all for that matter, so please use your vet’s guidance.
      Dr D

  10. Sharon on July 6, 2011 at 5:23 am

    What’s your opinion on the VDxI-TK canine blood test to detect hemangiosarcoma and lymphoa? Is it an accurate test?

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