Metastasis?

Question
I am a Certified Applied Animal Behaviorist, expert on this site for 7 years.  I have a 9-1/2 year old Toy Poodle.  On March 21, 2014, during routine (monthly) mammary screening (by touch), I discovered a lesion in her left inguinal teat.  On March 24, a mastectomy was done (just on that teat).  Biopsy came back cancerous but all tissue surrounding the growth appeared clear.  The tumor/mass was rocky and felt a bit smaller than the pad of my little finger, it had come out of nowhere in less than a month.

For the past two days, my bitch has been experiencing what appears to me to be urinary incontinence: again, out of nowhere.  She has urinated three times today indoors, once on my couch (this morning as I was getting ready to take her out).  She is now wearing "underwear" with a pad to prevent this from happening indoors.  I sold my house and now live an a luxury apartment building where this sort of thing might result in my eviction or the forcible re-homing of this dog.  I have an appointment with my veterinarian next Tuesday.

She is in good weight, otherwise behaves normally, but I've lost dogs to cancer so this means nothing to me right now.  The veterinarian consulted two pathologists: one at Cornell and the other at the Animal Medical Center, regarding the pathology report on the removed cancer.  Both advised a full line mastectomy should not be done and the chance of metastasis was quite low given the fact that I had caught the tumor so early.

I fear my dog now has bladder cancer.  Is it possible for this to have occurred in one year's time?  Thank you Doctor for your opinion.

Answer
It is quite common for older bitches to have urinary incontinence due to a weak detrussor muscle in the urethra.  We will often prescribe phenylpropanolamine (Proin Tablets) for that.  If there is no blood in the urinalysis, a Bladder tumor antigen test can be run to rule out bladder cancer.  An ultrasound or a bladder x-ray with contrast may show if there are irregularities of the bladder wall.