The five-term Republican said in a statement released by his office Tuesday that he was diagnosed with an early recurrence of Hodgkin's disease, which is a cancer of the lymph system.
Specter, 78, underwent treatment for the same type of cancer in 2005 and was later given a clean bill of health. The statement said that the cancer was revealed in a medical scan but that he has no symptoms.
"I was surprised by the PET scan findings because I have been feeling so good," Specter said in the statement. "I consider this just another bump on the road to a successful recovery from Hodgkin's, from which I've been symptom free for three years."
In his recent book, "Never Give In: Battling Cancer in the Senate," Specter credited hard work with getting him through the cancer treatments.
"An illness like Hodgkin's serves as a reminder that we have a limited time and how our time can end when we least expect it," Specter wrote. "Moreover, the event of death could never eclipse what is most important, which is how we spend the time we have."
The statement released by his office said tests showed cancer in lymph nodes in his chest. A follow-up biopsy of one of the chest lymph nodes was positive for recurrence.
Specter's oncologist, John H. Glick of the Abramson Cancer Center of the University of Pennsylvania, said in the statement released by the senator's office that Specter has an excellent chance of fighting the disease. The early diagnosis of his recurrent Hodgkin's disease has a five-year survival rate of 60 percent, the doctor said.
Specter, Pennsylvania's longest-serving senator, said he would continue his normal duties just as he did three years ago. He's already announced he will run for re-election in 2010, and he said the cancer won't stop him from that.
The senator was bald from his cancer treatments as he was playing a very public role chairing the committee that confirmed John Roberts as chief justice of the United States. During the long hearings, he drank Gatorade and frequently wiped his face with tissue. At the time, he underwent six months of chemotherapy.
Specter has long been an advocate of using federal dollars for cancer research and embryonic stem cell research. While bald, he offered himself up at a Capitol Hill news conference as someone who could benefit from stem cell research.
"I've got a new hairdo, which you can all observe, and that is indicative of a problem which may well be helped by stem cell research if it were to go forward," Specter said at the time.
The lymphoma recurrence was described as less advanced, and the statement said he will undergo three months of chemotherapy.
Specter had successful surgery for a brain tumor in 1993. It recurred three years later but was successfully treated. In 1998, he underwent bypass surgery and later suffered cardiac arrest.