"After several days of tests, I have been diagnosed with Diffuse Large B Cell Lymphoma, which is a serious but curable form of cancer," Raskin said in an official statement.

"I am about to embark on a course of chemo-immunotherapy on an outpatient basis at Med Star Georgetown University Hospital and Lombardi Comprehensive Cancer Center. Prognosis for most people in my situation is excellent after four months of treatment."

Raskin, who represents part of Maryland, oversaw the U.S. House's impeachment of Trump for "incitement of insurrection," finding that he encouraged the rioters who attacked the U.S. Capitol on Jan. 6, 2021. The House voted to impeach the president, but he was acquitted in the Senate, with 57 senators voting for his conviction, short of the 67 votes required to convict.

Raskin has also served on the January 6 Committee, which investigated the Capitol attack and Trump's role in it.

In the next Congress, Raskin is set to serve as the top Democrat on the House Oversight panel. In that capacity, he will butt heads with Republicans, who are expected to launch a number of contentious probes, including an inquiry into the business dealings of Hunter Biden, President Joe Biden's son.

In the Wednesday statement, Raskin said he expected to continue working, but that he had been advised by doctors to minimize unnecessary exposure to contagious viruses including COVID-19 during the treatment period.

(Reporting by Gram Slattery in Washington; Editing by Caitlin Webber and Matthew Lewis)

By Gram Slattery