The likeliest possibility here is mammary gland hyperplasia as a result of
the adrenal disease.  The increased estrogen can do it - it's certainly
not common, but I have seen in about five times over the years.  Please
get a photo if you can, and if a biopsy is ever taken, I'd be happy to
read it at no charge.
 
I am unfamiliar with any side effects of the medications that you mention
that would cause this.
 
With kindest regards,
Bruce Williams, dVM
[Posted in FML issue 3623]