Since the 2008 campaign began, doctors not connected with Mr. McCain’s case have expressed intense interest in the extent of the face and neck surgery that he underwent on Aug. 19, 2000, at the Mayo Clinic Scottsdale in Arizona.

Some of these doctors have noted in e-mail messages and in comments to reporters that the surgery appeared to be so extensive that they were surprised his melanoma was not more serious  perhaps Stage III, which would give him a bleaker prognosis. These doctors said they would be surprised to learn that such an operation would be performed without evidence that the melanoma had spread.

But a number of melanoma experts said in interviews that such an operation was understandable according to the medical standards of 2000 and that the extensive surgery did not necessarily imply Stage III melanoma.

“It was not out of line,” said one of the experts, Dr. Richard L. Shapiro, a melanoma surgeon at New York University. Dr. Shapiro added that he would feel more comfortable in making a judgment if he saw a full pathology report.

“It was a complex problem,” he said, “that was handled very skillfully by a team of experts.”

Dr. Denis Cortese, Mayo Clinic’s president and chief executive, said in a recent interview that experts in all three of the clinic’s sites discussed details of Mr. McCain’s operation before it was performed.

In trying to discover whether the melanoma had spread from his temple, Mr. McCain’s doctors made an incision down the side of his face and partly removed the lymph nodes in his neck, the campaign said in the statement.

“No spread of melanoma was found in any of these locations,” the campaign said. “However, this preventative procedure had cosmetic side effects for Senator McCain, including swelling at the site of the incision. Thus, the large scar and attendant swelling that Senator McCain has on the left side of his face is not the result of the melanoma itself, which was small and localized, but rather of the more extensive surgical procedure utilized out of a high degree of caution.”