Steve Scalise, the second most powerful Republican in the US House of Representatives, has announced he is being treated for cancer.
The House Majority leader said he had been diagnosed with multiple myeloma, a blood cancer.
"I expect to work through this period and intend to return to Washington," the Louisiana lawmaker said.
The 57-year-old survived a mass shooting in 2017 and underwent an extensive recovery.
Mr Scalise said in a statement on Tuesday that "after a few days of not feeling like myself this past week, I had some blood work done".
"The results uncovered some irregularities and after undergoing additional tests, I was diagnosed with Multiple Myeloma, a very treatable blood cancer," he said.
"I am incredibly grateful we were able to detect this early and that this cancer is treatable," he added.
"I am thankful for my excellent medical team, and with the help of God, support of my family, friends, colleagues, and constituents, I will tackle this with the same strength and energy as I have tackled past challenges."
Mr Scalise was elected to the US Congress in 2008 and has steadily risen through the ranks of Republican leadership.
He is currently right-hand man to House Speaker Kevin McCarthy, and his job is to keep the chamber's conservative majority in line.
In 2017, Mr Scalise was attending practice for a congressional baseball game when a gunman opened fire on the group, wounding five people.
Mr Scalise was shot in the hip. He underwent a months-long recovery and eventually returned to work, where he continued to serve in leadership positions.
On Tuesday, Republican colleagues noted Mr Scalise's previous recovery in messages of support.
"The same faith, family support, and internal strength that made Steve such an inspiration to others after he was shot, will bring him through this illness and once more inspire us all," Senator Bill Cassidy of Louisiana said in a statement.
Multiple myeloma is relatively uncommon in the US, according to the American Cancer society, with about 35,730 cases expected to be diagnosed this year.
The cancer affects plasma cells, the white blood cells that help with the body's immune response.
"Although there currently is no cure for this disease, it is treatable if detected early enough," Dr E Anders Kolb, head of the Leukemia and Lymphoma Society, said in a statement.
"Over the years, countless treatment advances have proven effective in reducing symptoms, slowing disease progression and prolonging life while preserving a patient's quality of life."
Three other members of Congress have undergone cancer treatment since 2022.
Democrats Jamie Raskin, Dan Kildee, and Joaquin Castro all disclosed their diagnoses.
Mr Raskin announced in April that he was in remission, and Mr Kildee said he had a "successful" operation this past spring.