"I was diagnosed with thyroid cancer in October and was forced to give up many of my regular duties as chief justice of the United States," the letter, from Chief Justice William H. Rehnquist, read. "But I have been able to resume some of them recently. I am happy to take this occasion to thank you and your associates for all of the help that you have given me."
With its upbeat tone, the letter, which has not been published, only adds to the mystery about the 80-year-old chief justice's medical condition and plans, a puzzle that has consumed not only official Washington but the medical community as well.
On Friday, rumors of an imminent retirement announcement by Chief Justice Rehnquist reached a frenzy of bizarre proportions. He was first said to have informed the White House that he would announce his retirement on Monday. The rescheduling from Monday until Tuesday of a meeting between the president and the Senate leadership was taken as proof of the chief justice's intention; in fact, the change was made to accommodate the schedule of Senator Bill Frist, Republican of Tennessee, the majority leader.
Then reports had the retirement being announced on Friday afternoon, after President Bush returned from Scotland. First one and then another of the associate justices were also said to be planning to leave the court.
Mr. Bush discussed potential court nominees on the trip back with his chief of staff, Andrew H. Card Jr., according to a pool report filed from Air Force One. Mr. Bush's press secretary, Scott McClellan, suggested that Mr. Bush had not yet narrowed that list, though the White House has been careful not to indicate how many candidates he is considering.
On Capitol Hill, meanwhile, lawmakers and senior aides of both parties said they had no notification or information of a vacancy besides Justice Sandra Day O'Connor's, though neither side would rule one out. All the while, Chief Justice Rehnquist remained at work in his chambers at the court, as he has every day since the court finished its term 11 days ago.
Thyroid experts around the country have been talking among themselves for months about the chief justice's illness and how well he seems to be doing. Some doctors unconnected with his case have inferred, from the treatment he has received, that he has the anaplastic form of thyroid cancer; if so, he has already defied the dire prognosis of that most aggressive form of the disease, usually measured in weeks or a few months, by being at work nine months after the diagnosis.
Many doctors predicted last fall that Chief Justice Rehnquist would never return to the court. But he was back in his chambers in December, after surgery in October to perform a tracheotomy, which created a hole in his windpipe to assist his breathing. He resumed attending the court's argument sessions in March.
Dr. Leonard Wartofsky, chairman of the department of medicine at Washington Hospital Center, said in an interview that he was "surprised Mr. Rehnquist has done so well." Dr. Wartofsky, a thyroid cancer specialist, said the chief justice's case was "a big topic" among thyroid experts. "It's on people's minds" and "we talk," he said. Another specialist, who had spoken to the chief justice's own doctors, said they were "very, very pleased about his course and that he is so on the ball."
Because Chief Justice Rehnquist's letter was addressed to a group of research-oriented doctors, members of the American Thyroid Association, it suggests that he may be receiving an experimental therapy that could explain why his treatment has yielded results better than expected.
Researchers are testing a number of drugs for anaplastic thyroid cancer. The drugs include those like Gleevec and irinotecan, which are marketed for different kinds of cancer, and novel compounds identified only by initials. The experimental drugs generally are in the earliest phases of testing for anaplastic cancer.
The court has never disclosed Chief Justice Rehnquist's precise diagnosis, which is a critical factor in judging the seriousness of a malignant tumor. Some doctors have complained that the limited information has made it difficult for them to answer questions from their own thyroid cancer patients. The doctors say that when these patients ask whether they have the same kind of cancer and whether they can get whatever treatment appears to be working for the chief justice, they can only guess.
"I don't understand why he has not provided a more specific diagnosis of the type of thyroid cancer," said Dr. Lewis E. Braverman, chief of endocrinology at the Boston University School of Medicine and an editor of a standard textbook on the diseases of the thyroid gland.
Dr. Kenneth D. Burman, director of endocrinology at Washington Hospital Center, said that he believed that Chief Justice Rehnquist had anaplastic thyroid cancer but that if he did not, "it would be important for people to know that."
Anaplastic thyroid cancer is rare, and Dr. Steven I. Sherman, chairman of the endocrine cancer department at the University of Texas M. D. Anderson Cancer Center in Houston, cautioned against jumping to the conclusion that this was the chief justice's diagnosis. "More likely it was not anaplastic thyroid cancer, just by the relative frequency of the other" types of the disease, Dr. Sherman said.
The fact that Chief Justice Rehnquist still has the tracheotomy is not necessarily a clue to the state of his health, either, doctors said. Dr. Burman said that in some cases, "you might leave the tracheotomy in because you really don't know what is going to happen in the future."
As Friday afternoon turned to Friday night without the retirement announcement that the columnist Robert Novak, the blogger Matt Drudge and others had predicted, attention shifted to the prospect of flurries of rumors throughout the summer. Supreme Court justices have typically timed their retirement announcements for late spring or early summer to enable a nominee to be confirmed and seated in time for the opening of the new term in October.
On Friday morning, reporters standing outside Chief Justice Rehnquist's suburban Virginia townhouse shouted questions at him as he emerged to be driven to work. Was there any truth to the retirement rumors, they asked.
"That's for me to know and you to find out," he replied.