Surgeons at Mayo Clinic Hospital in Phoenix "successfully removed the 5-cm blood clot during a minimally invasive craniotomy with an eyebrow incision," the statement said.
An eyebrow incision is not a big deal, explained CNN Chief Medical Correspondent and practicing neurosurgeon Dr. Sanjay Gupta, but the bone was opened to gain access to the brain, Gupta explained on CNN's New Day Monday.
"It's a significant operation," he said, adding that general anesthesia was used and "there was obviously an abnormality that was concerning enough for him to go through this."
Gupta prefers to refer to the clot as an "abnormality" because lab results are still pending and, "it's a pretty significant size of compression on that part of the brain."
But the location of the clot could be indicative of something more. "The operation seems to have gone well, but one thing worth noting is that Senator McCain has a history of invasive melanoma in and around that area," Gupta said.
The clot was over the senator's left eye, not far from the left temple where he was diagnosed with melanoma in 2000. The big concern is that this blood clot could signal a recurrence, according to Gupta.
"They're calling it a blood clot. When it's removed, you want to look at it specifically under the microscope and see if there's anything that indicated this could be melanoma. You try to remove this early and aggressively," he said.
The diagnosis in 2000 was not McCain's only history of skin cancer. He previously had three other malignant melanomas removed, on his left shoulder, left arm and left nasal wall (removed in 1993, 2000 and 2002 respectively). All were declared Stage 0, having been limited to the top layer of the skin, and were not invasive.
But the invasive melanoma in 2000 was the reason McCain has been regularly screened by his doctors. That's likely why the new issue was found during a routine screening, rather than as a result of the senator seeking care for specific symptoms.
McCain will spend this week recovering per doctors orders, his office said. Gupta noted that if McCain were his patient, he'd probably anticipate a couple of weeks to fully recover.
Senate Majority Leader Mitch McConnell announced Saturday that the Senate will delay consideration of the Republican health care bill
while McCain recovers from surgery.
Lab results are pending on the tissue around the clot. "Once the pathology information is available, further care will be discussed between doctors and the family," according to the statement.
Gupta was one of a select group of reporters who reviewed McCain's medical records
in 2008 when he was campaigning for president.