Jimmy Carter stood at the front of his beloved church in Plains on Sunday with some news for the 350 Sunday school students packing the pews: His most recent brain scan was clean. The cancer, he said, was gone.

Doctors caution that the former president is not completely out of harm’s way and he’ll continue treatment in hopes of keeping the disease from creeping back.

Still, it was a remarkable turn of events for the 91-year-old, who announced in August that melanoma cancer had spread to his brain and spoke with astonishing candor about what could be his final months. Many of his family and friends, some of whom had no idea the news was coming, were left grasping to explain the new diagnosis.

“It’s like getting the biggest Christmas gift that you could ever want,” said Jan Williams, who humorously instructs visitors on the do’s-and-don’ts of being around their famous teacher at Maranatha Baptist Church before each Carter lesson.

“This week was just horrible in the world in terms of all the bad things happening. How wonderful in the midst of all this to get such wonderful, encouraging news.”

The Atlanta Journal-Constitution broke news of Carter’s pronouncement early Sunday when a close friend and fellow parishioner alerted the newspaper.

Carter’s grandson, James Carter, who in August said he came to the hard truth that his famous grandfather was a mere mortal after the cancer diagnosis, had a different response on Sunday after the news broke about his cancer-free tests.

“See?” he added. “I knew he wasn’t really human.”

Or as his friend, Williams, put it: “I never felt God was through using Jimmy Carter yet. He’s done what the doctors told him to do, and what an example that is for the rest of us.”

Those doctors, from Emory University’s Winship Cancer Institute, deferred all requests for comment to the Carter Center on Sunday. Meanwhile, one expert who is not involved in the former president’s treatment cautioned that this latest bit of good news doesn’t mean he is cured or is totally cancer-free.

“It doesn’t mean that there is no cancer in his body; it means that there is no indication that they can find cancer for the present,” said Dr. Len Lichtenfeld, deputy chief medical officer for the Atlanta-based American Cancer Society, who stressed he was speaking about cancer in general.

While the scans of Carter’s brain and liver show no signs of the disease, cancerous cells could still be in his bloodstream, said Lichtenfeld. Still, he said, the news is encouraging for Carter.

“The President has done exceptionally well. There are still many patients with melanoma who don’t have this outcome,” said Lichtenfeld. “He’s in the best possible place.

Carter said in August that doctors had found four small melanoma lesions on his brain. The discovery followed the removal of a lesion on his liver that took about ten percent of the organ. He said he would receive four drug treatments, along with radiation therapy, and that he would cut back significantly on his schedule.

He’s since had a tide of encouraging medical news. At a Habitat for Humanity build in Memphis last month, Carter said he had completed his round of four treatments and was feeling good. A week later, the Carter Center said Winship doctors told their famous patient that he was “responding well to treatment.”

And on Sunday, after another round of tests at Emory last week, Carter came to his regular Sunday School lesson with the latest update.

“I went to the doctors this week for the second time. The first time I went for an MRI of my brain, the four places were still there but they were responding to the treatment,” he said in a video posted by NBC News. “When I went [for an MRI] this week they didn’t find any cancer at all. So I have good news.”

That’s when the cheers erupted and Carter, smiling in a jacket and a Bolo tie, turned toward the crowd.

“So a lot of people prayed for me,” he said. “And I appreciate that.”

The former president said in a statement Sunday that he will continue his treatment, which includes regular doses of Keytruda, an auto-immune drug designed to unleash the body's immune system to attack cancer cells. It's not clear what other test Carter's team at Winship conducted, and those close to him declined to comment on his next options.

In Plains, though, no one appeared to be holding back.

The mood around town was one of “elation,” said Plains Trading Post owner Phil Kurland. He said someone at the church had already come to his memorabilia store to relate Carter’s news. Over the next few hours, he said, people kept streaming in later in the day to express their wonder - and in some cases, slight apprehension.

“Apprehension in that they’re hoping (the news) stays good,” Kurland explained. “Certainly, though, the feeling is it’s a happy surprise.”

Even before this latest piece of good news, the former president was upbeat and active.

Another Carter grandson, former state Sen. Jason Carter, said Wednesday during an address to the Atlanta Press Club that his grandfather was doing well - physically, emotionally and mentally.

Jason Carter then noted that he took the job as the chair of the Carter Center after his grandfather said his cancer would force him to take a step back from his day-to-day duties.

“There’s been no evidence of that at all.”

AJC freelance writer Virginia Anderson contributed to this report

A timeline of former President Jimmy Carter’s cancer treatment

Aug. 3: A Carter spokeswoman said the former president is expected to make a full recovery after removing a small mass in his liver.

Aug. 12: Carter said recent surgery to remove a small mass on his liver revealed he had cancer in other parts of his body. He did not say where the cancer originated or how widespread it was.

Aug. 20: Saying he’s hopeful and “surprisingly at ease,” Carter holds an extraordinary press conference where he announces that doctors found four small melanoma lesions in his brain. He said he would fight the cancer but was clear-eyed about the challenges ahead. His treatment is to include radiation and doses of Keytruda, designed to unleash the immune system to fight cancer.

Aug. 23: Carter returns to Plains and his Sunday School lessons at Maranatha Baptist Church. “I intend to keep on teaching at Maranatha as long as I can do it, he said.

Oct. 8: Doctors gave Carter the go-ahead for a Habitat for Humanity build in Nepal, but organizers scrapped the trip due to unrest in the Asian nation.

Nov. 2: At a Habitat for Humanity project in Memphis, Carter said he was in good spirits and that he keeps up an active routine of bike riding, hiking in the woods and swimming in the covered pool located on their property in Plains.

Nov. 10: The Carter Center says Carter received “good news” from Emory physicians who found no evidence of new malignancy and that he is responding to treatment.

Dec. 6: Carter tells his church an MRI scan “didn’t find any cancer at all.” His office follows up with a statement saying he plans to continue his treatment

How We Got The Story:

Jill Venjoska began covering Jimmy Carter in August 2014 as the former president prepared to turn 90. Since then, she has made repeated trip to Carter’s hometown of Plains, listening as he taught Sunday school at his church and enjoying the town’s famous Peanut Festival. Venjoska has covered Carter’s cancer diagnosis this summer and traveled with him to Memphis this fall, where he participated in a Habitat for Humanity project.