Chief Justice William H. Rehnquist (search) may be back on the job next week, although some physicians questioned whether his treatment for thyroid cancer (search) would sideline him longer.

Rehnquist announced his cancer diagnosis on Monday through a terse statement at the Supreme Court (search). The disclosure caught even the closest court observers off guard and injected into the presidential campaign the issue of appointments to the high court.

The 80-year-old widower and longtime smoker underwent a tracheotomy (search) over the weekend and was expected to be released this week from the hospital.

About 23,600 people develop various types of thyroid cancer each year in the United States. The thyroid is a gland in the neck below the Adam's apple that produces hormones to help regulate the body's use of energy.

The Supreme Court statement did not say if Rehnquist has a treatable form of the cancer, or a fatal one.

With the limited information, doctors differed on his prospects.

"The tracheotomy is a clue that he probably has an unusual variety," said Dr. Yosef Krespi, chairman of otolaryngology at St. Luke's-Roosevelt Hospital in New York. "It has to be the aggressive type or complicated thyroid cancer for someone to have a tracheotomy."

Dr. Paul Wallner of the National Cancer Institute (search) said a tracheotomy, which involves opening the throat and inserting a tube, might be done for two reasons: "Simply in anticipation of routine thyroid surgery or ... because he was having breathing difficulty."

Rehnquist's hospitalization at National Naval Medical Center (search) in suburban Bethesda, Md., gave new prominence to a campaign issue that has been overshadowed by the war on terror. The next president probably will name one or more justices to a court that has been deeply divided in recent years on issues as varied as abortion and the 2000 election itself. President Bush won that after the Supreme Court issued a key 5-4 decision in his favor, with Rehnquist as part of the majority.

The last court vacancy was in 1994, the longest stretch of continuity in modern history. Only one of the court's nine members — Clarence Thomas, appointed by former President Bush — is under 65.

"This court has grown old together," said Edward Lazarus, a Los Angeles attorney and former Supreme Court clerk.

Rehnquist, a conservative named to the court in 1972 by President Nixon and elevated to chief justice by President Reagan in 1986, has had a series of health problems, including chronic back pain and a 2002 torn leg tendon that required surgery.

He was admitted to the hospital Friday and doctors performed the tracheotomy Saturday.

The court did not explain why it was done, or say if Rehnquist also had the more common treatment, the removal of the thyroid.

Lazarus said the secrecy was not surprising.

"The court doesn't appreciate being at the center of the political storm. It's an uncomfortable situation," he said.

If Rehnquist is too sick to participate in any cases, the other eight justices will act without him. Any tie votes would uphold the lower court decision.

Three other justices have had bouts with cancer. Justice John Paul Stevens (search), the oldest at 84, was treated for prostate cancer. Justice Sandra Day O'Connor (search) had breast cancer and Justice Ruth Bader Ginsburg (search) colon cancer.

Rehnquist turned 80 this month. The only older chief justice was Roger Taney, who presided over the Supreme Court in the mid-1800s until his death at 87.

No matter who is elected president next week, a vacancy on the high court is likely during the next presidential term. And confirmation for any nominee is bound to be contentious due to the close split in the Senate. Bush and Kerry have avoided describing a litmus test for a Supreme Court nomination, although their differences on abortion are cut along partisan lines. The future of Roe v. Wade, the three-decade-old ruling that affirmed the legality of abortion, is the most visible symbol of the court's ideological split.

Monday's statement said that Rehnquist was expected on the bench next week when the court meets next to hear arguments.

Dr. Kenneth Burman, a thyroid specialist at Washington Hospital Center, said routine thyroid surgeries require an overnight hospital stay and involve a relatively quick recovery time. Thyroid cancer is generally more aggressive in older patients, he said.

Krespi said he would not recommend a cancer patient who needs a tracheotomy return to work so quickly.

Word of the illness comes as the Supreme Court deals with multiple legal fights stemming from the extremely tight election campaign. On Saturday, the court refused to place independent presidential candidate Ralph Nader on the ballot in Pennsylvania. The high court has not yet acted on a similar appeal from Nader involving Ohio.

Concerns have arisen that the outcome of the presidential election could be challenged again, perhaps all the way to the high court.