Lump under arm of puppy.

Dr. Marie replied:

Thanks for your question.

It would be extremely unlikely for a lump on a 10 week old puppy to be cancer. In 13 years of practice I can't say I have ever seen a puppy that young have a cancerous lump like you have described.

Is there any chance that any of Eclipse's vaccinations were given in that spot? It is a little bit of an unusual spot, but sometimes we do give injections on the side of the chest. It's possible his was a little further forward than normal (which can happen with a squirmy puppy).

If so, then this could be something called a vaccine granuloma. Vaccine granulomas almost always go away on their own but can take a month or two to do so. The textbooks tell us that they can sometimes become cancerous but it is very very rare for this to happen.

I have seen some unusual unexplained lumps on puppies that just go away on their own as well. Some of them could be perhaps scar tissue from a bite from a sibling or some other accident.

A lymph node really should have been easy to diagnose (as the cells all look like lymphocytes) and an infection/abscess should have been easy as well.

I think it is the right thing to do to send this sample to a pathologist just to be sure, but I'm guessing the diagnosis will be one of two things:

1. Vaccine granuloma - in which case we just wait and see and it should go down in a few days to weeks.

2. Diagnosis open - The pathologist may say, "Hmmm....I really don't know what this is but it's not likely to be anything to worry about."

Hopefully you will get some results soon but I will be absolutely shocked if this is cancer.

Dr. Marie.

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Dr. Marie replied:

If it was the back leg, then it's not likely to be a vaccine granuloma. But some random scar tissue is still possible.