It is a classic good news, bad news situation. The good news: Argentine President Cristina Fernandez didn't have cancer after all. The bad news: her doctors didn't find out until after they had completely removed her thyroid gland. 

"Tissue studies ruled out the presence of cancerous cells in the thyroid, thus modifying the initial diagnosis," presidential spokesman Alfredo Scoccimarro said Saturday.

Fernandez doesn't even have to swallow the radioactive iodine that patients usually take after thyroid cancer surgery, to make sure any remaining cancer cells are killed, her spokesman said. But she will have to take hormone medicine for the rest of her life.

Fernandez returned Saturday to the presidential residence in suburban Olivos. She underwent the surgery Wednesday, just 25 days after beginning her second term.

The 58-year-old president, through her spokesman, thanked the medical team led by the hospital's surgery chief, Dr. Pedro Saco, an expert in cancers of the head and neck. Later Saturday, she added her own thoughts in a tweet, saying: "Now from Olivos, we thank all the people, citizens, activists and personalities, for the signs of affection and concern."

The announcement that she is cancer-free prompted raucous cheers and chants from several hundred supporters holding vigil for days outside the hospital, carrying signs saying "Be Strong Cristina!"

The idea that she had cancer had worried many Argentines, who re-elected her with a 54 percent landslide in October in part because none of her rivals seemed as capable of maintaining economic growth and social stability.

Since she and her late husband and predecessor as president, Nestor Kirchner, began governing in 2003, Argentina has come back strong from a disastrous world-record debt default and currency devaluation a year earlier. The economy has grown at an average annual rate of 7.6 percent, poverty and unemployment are down and the wealth gap has narrowed.

Their administrations have transferred billions of dollars to the poor through social programs.

But their style of rule has been highly personal, concentrating power in a very small circle of loyal advisers. Kirchner's sudden death of a heart attack in 2010 during his wife's first term left many Argentines worried about whether Fernandez could maintain the couple's model of governing, and the cancer diagnosis renewed those fears.

Without her thyroid gland, Fernandez now faces a lifetime of hormone replacement therapy.

This might have been avoided had doctors removed only half of her thyroid, the part surrounding the apparently cancerous nodule, said Dr. Robert Haddad, chief of head and neck oncology at the Dana Farber Cancer Institute in Boston.

"That's the downside. If you remove only half, you don't need the replacement therapy," Haddad said. "It's a pill you take once a day, just like a pill for blood pressure or something, but you have to take it for the rest of your life, which is not insignificant."

Preoperative thyroid cancer diagnoses usually involve inserting a needle and removing a few cells from the suspicious lump.

When tests come back positive for cancer, it's best to repeat the test and to get a second opinion before surgery, Haddad said. Still, the only way to be sure a growth is benign or malignant is to remove at least part of the gland.

Some doctors and patients opt for removing the entire gland just to be sure, but Haddad said thyroid cancers tend to be so "well-behaving" that taking the more drastic step usually doesn't make sense.

"If five years down the road she develops cancer in the other lobe, her prognosis remains excellent. So there's not really a downside in waiting, in terms of outcome and diagnoses, because we're dealing with such a highly curable cancer here," Haddad said.

Dr. R. Michael Tuttle, an endocrinologist at the Memorial Sloan-Kettering Cancer Center in New York, is chairman of a network of experts that writes the U.S. guidelines for dealing with thyroid cancers, has traveled to Argentina and has seen its quality of care. He says the president's team did nothing wrong.

"What I would assume was that the biopsy they did was read as papillary thyroid cancer, and 98 percent of the time they'd be right," Tuttle said.

"This two percent miss rate happens everywhere in world ... it happened to me last year," he added. "Argentina has some of the leading thyroid cancer people in the world, so I don't have any doubt that she was in really good hands."

This article is based on reporting form the Associated Press.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino