WASHINGTON (AP) - Missouri Sen. Claire McCaskill says she has breast cancer. 

The Democratic senator said in a blog post Monday that the cancer was detected through a regular mammogram and she will be in St. Louis for the next three weeks receiving treatment. She said "it's a little scary" but her prognosis is good and she expects a full recovery.  

McCaskill said she will post on her website how she would have voted on any matters that come before the Senate while she is gone.