Missouri Democrat Sen. Claire McCaskill announced on her social media accounts that she has breast cancer on Monday, a disease she says was detected through a routine mammogram.
McCaskill, 62, said that she would spend the next three weeks in St. Louis receiving treatment.
She directed readers to her website for a record on how she would have voted on issues that may come before the Senate during her absence and plans on submitting questions for hearings she may miss.
This article originally appeared on NBCNews.com.