WASHINGTON, April 15 (Reuters) - Republican Sen. Arlen Specter said on Tuesday he has been diagnosed with a recurrence of Hodgkin's disease, a cancer of the lymph system, but expected to continue working and campaigning for re-election in Pennsylvania.

Specter, the ranking Republican on the Senate Judiciary Committee, was originally diagnosed in with Hodgkin's in 2005 and received six months of chemotherapy, achieving complete remission for three years.

The disease is at a lower level this time and he will now undergo chemotherapy weekly over the next 12 weeks, the 78-year-old senator said in a 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 3 years," Specter said, adding that he was surprised by the discovery because he had been feeling so well.

His doctor, John Glick of the University of Pennsylvania, said Specter "has an excellent chance of again achieving a complete remission of his Hodgkin's disease."

Specter had successful surgery for a brain tumor in 1993, which recurred in 1996 and was successfully treated. In 1998, in the middle of a re-election campaign, he underwent bypass surgery and post-operatively suffered cardiac arrest, from which he recovered.

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