USTIN, Texas - Senator John S. McCain has been diagnosed with melanoma, a form of skin cancer that is highly curable if found early, but that quickly turns lethal if allowed to spread.
In a statement released yesterday, McCain's office said two spots, one on his left arm and another on his left temple, had been discovered in a routine exam. ''The spots were confirmed to be melanomas,'' the statement said.
It is the second such diagnosis for the Arizona Republican, who had a cancerous mole removed in 1993.
The diagnosis, which has forced McCain to cancel several campaign appearances, confirmed suspicions among some people traveling with him in recent weeks that he is ill.
McCain, the Vietnam War hero who made a spirited run for the GOP presidential nomination this spring, did not make any public comments yesterday. His last appearance was Sunday, when he hosted Governor George W. Bush at his Sedona, Ariz. vacation home.
The diagnosis was made after a biopsy Aug. 4 at the National Naval Medical Center in Bethesda, Md. McCain wore a bandage over his left temple during his campaigning with Bush. At the time, McCain kept the diagnosis quiet, saying only that he had a growth removed.
But he did mention the disease. Noting that the campaign swing would bring the Bush entourage through Arizona, McCain told reporters that his home state has ''the highest incidence of skin cancer of any state in the union.''
''I advise everyone: Wear sunscreen,'' McCain said.
McCain, who spent yesterday at his Phoenix home, is planning to hold a press conference to discuss his health. He hopes to make his remarks after undergoing tests today and tomorrow at the Mayo Clinic near Phoenix, where he will determine his course of treatment, sources said.
Senator John F. Kerry, attending the Democratic National Convention in Los Angeles, spoke yesterday with McCain's wife, Cindy. She said her husband ''is in very good spirits'' and planned to call Kerry later, the senator said, adding that a ''procedure'' may be done at the end of the week.
McCain, who will turn 64 this month, released his medical history this year in an effort to dampen rumors that his 51/2 years as a prisoner of war in Vietnam had affected his mental health.
In the process, he also said a cancerous mole had been removed from his shoulder in 1993. That incidence of melanoma had not spread, and had not penetrated deep into his skin, and doctors had cleared McCain as healthy.
The news of McCain's diagnosis yesterday prompted a flurry of wishes for his speedy recovery from colleagues, many of whom saw him two weeks ago, when he was a featured speaker at the Republican National Convention in Philadelphia.
Bush, who waged a fierce battle against McCain in the primaries before reconciling with the senator and inviting him on the campaign trail, issued a statement from his vacation home in Crawford, Texas, wishing his former rival well. The two men did not speak to each other yesterday, said a Bush spokesman, Ari Fleischer.
''I know all Americans join Laura and me in wishing John McCain a speedy recovery,'' the statement from Bush said. ''We just came back from a visit to John and Cindy's home and our fondest thoughts are with him and his family. John is a good man and a fighter.''
Boston-area doctors were reluctant to comment on McCain's prognosis without knowing details of his condition, but said the most important factor is how thick the melanomas had grown.
''If you catch it early, it's nearly 100 percent curable. If it's let go, it can approach 100 percent fatal,'' said Dr. Thomas Rohrer, director of dermatologic surgery at Boston Medical Center.
People who develop one melanoma are about five times as likely as the general population to develop a second one in their lifetime, said Dr. Michael Atkins, an oncologistspecializing in melanoma at Beth Israel Deaconess Medical Center. ''But because they're being screened, oftentimes the subsequent melanomas are picked up earlier, and the chance is better.''
Melanoma is the least common of the three major skin cancers, but potentially the most lethal. Around 44,700 new cases of melanoma are expected in the United States this year, with about 7,700 deaths, Atkins said.
According to Roher, melanoma is the leading cause of cancer death for women between the ages of 25 and 30.
Eighty percent of melanomas can be cured with surgery alone, Atkins said. But the thicker they grow, the greater the chance the cancer has spread to the lymph nodes. If it is found there, Atkins said, there is a 40 to 80 percent chance it has spread to other organs, which makes it ''almost invariably fatal.''
Frank G. Haluska, director of melanoma programs at Dana Farber/Partners CancerCare, said it is important to know whether McCain's melanomas are new ones or recurrences of the original cancer, which would be more serious.
Doctors stressed the need to wear sunscreen and protective clothing and to get moles examined.
Kornblut reported from Austin, Barnard from Boston. Tina Cassidy of the Globe Staff contributed from Los Angeles.
