ER star Maura Tierney has revealed that she is preparing to undergo surgery to have a breast tumour removed.

Tierney is due to star in a new TV show ‘Parenthood’ and production has been halted to allow her time to convalesce.

“I have discovered a tumour in my breast which requires surgery,” Tierney said in a statement.

“I will not know either my exact diagnosis or course of treatment until that surgery is performed. I’m very optimistic as to the outcome.”

She said that NBC – who are producing Parenthood – had caused “confusion and undue alarm” by announcing that filming had been delayed.