The last thing Maggie Felmlee expected to hear at her annual gynecological appointment was that she had a “mass” on her thyroid that she should have checked.

“I was like, ‘Excuse me?’” the Carroll Twp. resident recalled. “My doctor said it was probably nothing, but I’m a nurse working in oncology, and she said the word ‘mass.’”

As it turned out, it wasn’t “nothing.” Felmlee, an otherwise healthy, 32-year-old woman, was diagnosed with thyroid cancer. The thyroid is a quarter-sized organ at the base of the throat that uses iodine to make hormones that help control heart rate, body temperature, metabolism and calcium in the blood.

“The good news was that it was papillary thyroid cancer, which is the most common and most treatable kind,” said Felmlee, now 39. “I couldn’t really believe it. Had my doctor not found the lump, I never would have known. It was so small that you couldn’t feel it unless you were looking for it.”

Though not a common cancer — about 44,000 Americans will be diagnosed this year, according to the National Cancer Institute — thyroid cancer rates are increasing, said Dr. David Goldenberg, head and neck cancer surgeon and head and neck disease team leader at the Penn State Cancer Institute in Hershey.

“While many other cancers are on the decline, thyroid cancer is on the rise, and no one is sure why,” he said. “Perhaps it’s because we have better early detection due to new technology such as a high-resolution ultrasound that can detect much smaller nodules than before.”

However, some experts speculate that thyroid cancer is on the rise due to exposure to low-dose radiation with a latency period of 15 to 30 years, he said. Up until the late 1950s, for example, people with acne and enlarged tonsils were treated with radiation, he said.

Pennsylvania has one of the highest rates of thyroid cancer in the country, said Goldenberg, who recently received a grant to look at the severity of thyroid cancer cases in central Pennsylvania as compared with the rest of the state.

“Thyroid cancer is a woman’s disease. It’s less common in men, and when you see it in men, it’s more aggressive than in women,” he said.

Thyroid cancer often doesn’t present with any symptoms. Most patients are diagnosed through a screening and ultrasound or incidentally when having a scan for another complaint such as neck pain or upper chest issues, which will show a nodule — the vast majority of which will turn out to be benign, Goldenberg said.

Felmlee had a thyroid scan prior to a needle biopsy of the nodule in her neck, which showed cancer. Though she could have had only the left side of her thyroid removed, where the lump was located, she opted to have the entire thyroid removed. Felmlee then went on a thyroid replacement therapy called synthroid.

Sometimes thyroid cancer spreads to adjacent lymph nodes and, if so, surgeons will also remove lymph nodes in the neck, Goldenberg said.

After surgery, Felmlee waited six weeks then was treated with radioactive iodine in the form of a drink. Two weeks prior, she ate a very low-iodine diet. “Since my iodine was so depleted, any thyroid tissue left would suck up the radioactive iodine. If any thyroid cancer tissue was left, the iodine would kill it off when I drank it,” Felmlee explained.

Subsequent scans showed no residual tissue. Now, Felmlee gets blood work done annually to test levels of thyroglobulin, a protein made by the thyroid. Since she had her thyroid removed, the protein should not be present, so a measurable level could signal a recurrence.

The best thing about thyroid cancer is that it’s very treatable. The cure rate is more than 90 percent, and it usually doesn’t recur, Goldenberg said. About 1,700 people will die from the disease this year, according to the National Cancer Institute.

Felmlee, who now has two daughters, ages 6 and 4, with her husband, Kevin, said she doesn’t expect the cancer to return and doesn’t feel like she lives under its shadow.

“The nurse in me knows there’s always a chance it could come back, but I don’t worry about it,” she said. “I feel very fortunate.”