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Rosie O'Donnell announced Friday that she has postponed her wedding to Michelle Rounds after her fiancée was diagnosed with a cancer-like disease that causes painful tumors.

Rosie posted a brief Twitter message that links to a longer blog post on Michelle's condition, which she said she wanted to publicize before word got out to the media. "b4 the tabloids run it," she tweeted.

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In her blog message written in poetic style, Rosie explains how Michelle's condition began. "On mothers day... morning pain… that won't let up." She reveals that Michelle was eventually diagnosed with extremely rare desmoid tumors, which she describes as "odd and curious beasts" that are non-cancerous but spread in the same way.

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She reveals that Michelle had surgery in June and that she's "getting stronger every day." She also said she's joined the fight against the disease and pledged to help raise awareness and money. O'Donnell said the wedding has been scheduled for next summer and encourages donations in lieu of gifts.

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Rosie-- who announced her split from former partner Kelli Carpenter in 2009 -- announced last December that she and Michelle were engaged.