Desmoid tumors are rare, with only 900 people per year in the United States diagnosed with the sometimes fatal growths.

The condition has gained attention in recent days because Rosie O'Donnell's wife, Michelle Rounds, had surgery to treat desmoid tumors just before getting hitched to the comedian in June.

O'Donnell is also raising awareness of desmond tumors after announcing she would be selling paintings on her blog to benefit the Desmoid Tumor Research Foundation. The high bid for one of the paintings on eBay was $730 as of Monday afternoon.

O'Donnell made the announcement on her blog Monday as she detailed her wife's condition:

"[M]y wife michelle/was diagnosed with desmoid tumors in june/a mysterious rare - too often fatal disease/that affects 3 in a million people," the actress and comedian wrote. "[We were to wed 10 days ago/but her illness forced us to postpone the wedding/luckily -/as i was in ICU that day."

What exactly are demoid tumors?

The growths form from fibroblasts, a type of cell that helps heal wounds and protects the lung, liver, blood vessels, heart, kidneys and other vital organs, according to the Desmoid Tumor Research Foundation.

The prognosis for desmoid tumors depends on how aggressively they grow and whether the growths compress organs such as the intestines, kidneys and lungs or blood vessels or nerves. More aggressive desmoids can be fatal, according to the foundation.

Unlike some cancers, desmoid tumors do not metastatize, meaning they don't spread from organ to organ or through the blood.

Desmoid tumors are extremely rare, with 900 people diagnosed with the condition each year, according to the foundation, although more people may have the condition due to difficulties diagnosing the growths.

Anyone can become afflicted with desmoid tumors, but they commonly occur in people in their 30s and 40s. Women are twice as likely to be diagnosed with desmoid tumors as men, according to the foundation.

There may also be a link between desmoid tumors and people who have a family history of colon cancer, according to the Mayo Clinic.

The growths are diagnosed through a biopsy and are treated either through surgery (as in Rounds' case), chemotherapy, radiation, medications and hormone therapy.

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