Frank Lautenberg — at 86 the nation’s second-oldest senator — has curable stomach cancer, his office revealed yesterday.

Doctors said the New Jersey Democrat would be treated for B-cell lymphoma over the next few months. Lautenberg, meanwhile, does not plan to resign, said spokesman Caley Gray.

He’ll undergo six to eight chemotherapy treatments, return to work between treatments and should make a “full and complete recovery,” said Dr. James Holland, of Mount Sinai Medical Center in Manhattan.

Lautenberg was hospitalized Monday after falling and was found to have a bleeding ulcer. Doctors stood by that diagnosis.

Under New Jersey law, Gov. Chris Christie, a Republican, would appoint a replacement should Lautenberg leave office.