Congresswoman Sheila Jackson Lee, a Democrat who represents Texas' 18th Congressional District, has been diagnosed with pancreatic cancer, she announced in a statement Sunday night.

"My doctors have confirmed my diagnosis of pancreatic cancer," Jackson Lee said. "I am currently undergoing treatment to battle this disease that impacts tens of thousands of Americans every year."

The 74-year-old said that the treatment would mean she would likely be "occasionally absent from Congress" but said she will work with Congressional leadership "to serve this nation and be present for votes on legislation that is critical for the prosperity and security of the American people."

Jackson Lee's district includes parts of Houston and she has served as its representative for almost 30 years. She unsuccessfully ran for mayor of the city last year, but lost to then-State Senator John Whitmire, also a Democrat. She faced a primary challenge for her congressional seat this year, but won that contest easily.

Jackson Lee did not provide details on the severity of the cancer or what her treatment will be. Pancreatic cancer is not often found in the early stages and tends not to present symptoms until it has advanced, according to Mayo Clinic.

More than a decade ago, in 2012, Jackson Lee revealed that she had undergone treatment for breast cancer, including surgery, chemotherapy and radiation, and had made a full recovery. Since then, her work in Congress has included securing millions of dollars in increased funding for breast cancer research.

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• Sheila Jackson Lee
• Pancreatic Cancer

Jordan Freiman

Jordan Freiman is a news editor for CBSNews.com. He covers breaking news, trending stories, sports and crime. Jordan has previously worked at Spin and Death and Taxes.