Sen. Frank Lautenberg, at 86 the nation's second oldest U.S. senator, has curable lymphoma of the stomach, his office said Friday.
Doctors for the Democrat found B-cell lymphoma that will require treatment over the next few months, spokesman Caley Gray said in a news release.
Lautenberg will undergo six to eight chemotherapy treatments and should make a "full and complete recovery," said Dr. James Holland of New York City's Mount Sinai Medical Center.
Lautenberg was taken to the hospital Monday after his office said he fell. The office said Tuesday the senator was treated for a bleeding ulcer.
He is expected to return to work at the Senate between treatments, Holland said.
A resignation could hurt the Democratic Party. Under New Jersey law, Gov. Chris Christie, a Republican, would be able to appoint a replacement if a senator left office.
The liberal Lautenberg became prominent as a founder of the payroll services company Automatic Data Processing long before he entered politics in 1982 with a successful run for the U.S. Senate.
He retired from politics and did not seek re-election in 2000, but returned two years later as a last-minute replacement in a Senate race when Sen. Robert Torricelli dropped out. He was re-elected in 2008.
He is a major supporter of gun control and a big critic of the tobacco industry.
Lymphoma is an immune system cancer, and the B-cell form is a type of the non-Hodgkin's lymphoma that strikes more than 65,000 people in the U.S. annually.
There are multiple subtypes of the B-cell form, with widely varying treatments and prognoses. Lymphomas can strike in lymph tissue anywhere in the body, such as the lymph nodes — and the stomach contains lymphoid tissue.