Most people know very little about their thyroid at all, let alone the health problems that can affect it. (The thyroid gland is in your neck, by the way.) But thyroid cancer is being talked about today more than ever, thanks to celebs like Brooke Burke-Charvet and Sophia Vergara, who both had the disease, and Robert Ebert, who died in 2013 after fighting thyroid and salivary cancer for years. Now Shark Tank star Daymond John has revealed that he was diagnosed with stage II thyroid cancer, and underwent surgery to have a nodule removed. "I have to monitor it for the rest of my life," John, 48, said on Good Morning America Wednesday. "I have another half of my thyroid still in. In the event it comes back I will have to fight it."

Rates of thyroid cancer have increased three-fold in the last three decades in the United States; by some measures, it's considered the fastest-growing cancer among women. To learn more, we talked with Hossein Gharib, MD, professor of medicine at the Mayo Clinic College of Medicine and former president of the American Thyroid Association. Here’s what he thinks everyone should know about this disease.

Diagnosis rates are up—but incidence isn't

Just because more cases of thyroid cancer are being caught by doctors, that doesn't mean more people are getting the disease. The increase in diagnoses is mostly due to better detection of small papillary thyroid cancers by ultrasound and biopsy technology, says Dr. Gharib. This sounds like a good thing, but it’s not without controversy: “Some consider this overdiagnosis of disease that is not clinically important,” he says, noting that many thyroid cancers are slow growing and not life-threatening. “Therefore, some patients undergo unnecessary treatment.”

Just this week the U.S. Preventive Services Task Force concluded that the harms of thyroid cancer screening outweigh the benefits, and recommended against screening adults who show no symptoms.

Symptoms are subtle—or non-existent

Some thyroid diseases—like hypothyroidism, or underfunctioning thyroid—can cause fatigue and weight gain. But thyroid cancer is usually more subtle, says Dr. Gharib. “It is commonly diagnosed when a patient presents with a thyroid lump or nodule,” he says. “Nodules are usually discovered incidentally, by the patient or by a doctor.”

Thyroid cancer is almost always treatable

Thyroid cancer is sometimes described as a “good” type of cancer to have (if there is such a thing) because most patients can be treated and live a relatively normal life. In fact, the 25-year survival rate for patients with papillary thyroid cancer, the most common type, is 95%.

RELATED: 19 Signs Your Thyroid Isn't Working Right

...But some forms are more aggressive than others

The age and family history of a patient, and the size of his or her tumor (as well as whether it’s spread to other organs), may determine how treatable, or how dangerous, the disease is. The type of cancer is important, too: “Follicular thyroid cancer accounts for only 10% but has a more guarded prognosis,” says Dr. Gharib, “and anaplastic thyroid cancer, a rare tumor, is very aggressive with very high mortality.”

Patients need follow-up care

Treatment usually involves removing the entire thyroid, an organ that produces vital hormones our bodies need to function properly. Because of this, thyroid cancer survivors need to take medication (usually via a daily pill) for the rest of their lives to replace these hormones. And because thyroid cancer frequently spreads to the lymph nodes, many patients experience recurrences and require a second or third surgery, says Dr. Gharib.

Radiation exposure is a risk factor

Thyroid cancer is more common in women, people with a family history, and people who have been exposed to radiation, especially as children. (X-rays deliver radiation in small doses, and are generally considered safe, although children should be exposed only when necessary.) A 2014 Japanese study revealed that 57 children living near the Fukushima nuclear power plant that was damaged in 2011 had been diagnosed with thyroid cancer, and 46 were suspected to have the disease, as well.

A lump doesn’t mean cancer

Discovering a nodule on your neck is not an automatic diagnosis of thyroid cancer, says Dr. Gharib, and up to half of all adults have them. Of these, only about 5% are malignant. “Thyroid cancer is uncommon,” he says. “When a nodule is discovered, referral to an endocrinologist is important for a careful evaluation.” And as long as it’s confirmed as benign, simple observation and follow-up is likely all the care you’ll need.