Sen. Claire McCaskill (D-Mo.) has revealed that she has breast cancer — found in a routine mammogram, NBC News reports.

McCaskill, 62, said she will be absent from Congress for three weeks while she undergoes treatment in St. Louis.

"I very recently learned that I have breast cancer. It was detected through a regular mammogram," she wrote on her Tumblr account. "It's a little scary, but my prognosis is good and I expect a full recovery."