U.S. Sen. Claire McCaskill announced Monday that she has recently been diagnosed with breast cancer.

In a post on the “tumblr” Web site, the Missouri Democrat said the cancer was detected through a regular mammogram. She said her prognosis is good and she expects to make a full recovery.

“I will be in St Louis for the next 3 weeks receiving treatment,” Sen. McCaskill said online. “During this time my staff will continue to assist Missourians and I will be posting on my Senate website (McCaskill.senate.gov) how I would have voted on any matters that come before the Senate during my absence—which I’ll also enter into the Congressional record. ”

“Thank you for the honor of serving you in the Senate.”

McCaskill also noted she would submit questions in writing for any missed Senate hearings.