What Causes Blood In Urine?

I had a hysterectomy 2 years ago this July, uterus and cervix. Metaplastic triple negative breast cancer diagnosed April 2014, 6 mths out from chemo and 4 from radiation. Tonite after peeing the toilet paper is definitely pink. I've noticed it a couple of times recently, but most obvious this time. Scared to death cancer is laying somewhere else. Other explanation ?