canine mammory tumors

Question
How could a mammary tumor show up less than a month after being pronounced tumor free? That is the situation with a 10-year-old chi I am trying to adopt from the shelter. She was a stray so I just now got to know her. If she had been mine she would have been spayed early! What are the chances of these tumors being benign?

Answer
Hi Shirley...

When you say that she was pronounced tumor fee, that brings up a number of questions for me.  Was she suspected of having a tumor and did they do a fine needle aspirate or something which they used to conclude that this dog was free of a tumor?  That method has been known to lead to erroneous conclusions, so I'm wondering if that's what happened?.

Shirley, take a look at this link for The Merck Veterinary Manual which vets rely on and you will see that it says that over 50% of canine mammary tumors are benign.

http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/112300.htm

I hope that helps.  Maybe you could get back to me and let me know how it was determined less than a month ago that she was tumor free?

Jo Ann