U.S. Senator Frank Lautenberg (D) of New Jersey has 'curable' stomach cancer, according to his office.

Spokesman Caley Gray said doctors for the nation's second-oldest U.S. senator found B-cell lymphoma of the stomach. His office said the tumor is "curable" and will require treatment over the next few months.

Dr. James Holland of New York City's Mount Sinai Medical Center said Lautenberg will receive six to eight chemotherapy treatments. The doctor said he expects a "full and complete recovery."

Lautenberg, 86, was admitted to a hospital on Monday after becoming lightheaded and falling at his home in Cliffside Park.

His office said Lautenberg underwent a successful endoscopy procedure.

Lautenberg was in great spirits, was joking with doctors, and would stay there overnight for routine observation, according to his office.

Lautenberg was first elected to the Senate in 1982. He retired in 2000 but was called back in 2002 as a late replacement for Sen. Robert Torricelli. Torricelli abandoned his re-election bid amid an ethics controversy five weeks before Election Day.