Swollen glands

Our 10 mth. old chihauhau, who is not pregnant has swolen m ilk glands almost hard, but only the lower ones, the ones high up on her chest are fine.  Is this a sign of something more serious, like cancer, she eats and acts fine otherwise?

[Aleda M Cheng, D.V.M., C.V.A]

She could have a form of pseudocyesis or false pregnancy if she is not spayed.  A false pregnancy can occurs after a heat cycle due to aberrant hormonal stimulation. It is not a serious condition but can be a nuisance.  It should go away on it's own but if it doesn't she may need hormonal treatments.  

Mammary gland cancer would be extremely rare in such a young dog.  Spaying your dog before her fourth heat cycle would reduce the risk of mammary gland cancer and would also stop subsequent false pregnancies.