Michelle Rounds and Rosie O'Donnell (WENN.com)

Actress and U.S. TV and radio personality Rosie O'Donnell has halted her wedding plans to allow her partner time to recover from surgery to remove rare desmoid tumours.

Michelle Rounds was diagnosed with aggressive fibromatoses earlier this year and she underwent surgery in June.

The diagnosis came after Rounds struggled with a "mystery illness" for months.

Posting news about her fiancee's health crisis on her blog earlier this year, O'Donnell wrote, "We wander thru (sic) the maze of medical mystery confused... It seemed impossible no one knew what was wrong."

Returning to her blog on Friday, O'Donnell confirms the diagnosis, calling the tumours "odd and curious beasts" and adding that they are "a non cancer that acts cancerous".

She tells fans her partner is "recovering from surgery in June, getting stronger every day".

The A League of Their Own star became engaged to Rounds at the end of 2011. They have postponed their wedding until next summer.