I Went In For A Physical A Few Weeks Ago

I went in for a physical a few weeks ago and I just got my blood work results back. All is great, little low on vitamin D. But I also got a stool sample test kit in the mail the following day. I have never had to do one of these before. Why would my Dr. decide to have this test done. I am a healthy 42 year old Female and was expecting a request for a mammogram.