Maura Tierney Maura Tierney

Maura Tierney is having surgery to remove a breast tumor, she said in a statement to

The surgery is the reason NBC is delaying production on her new series, Parenthood, by eight weeks.

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"I have discovered a tumor in my breast which requires surgery," the actress, 44, said. "I will not know either my exact diagnosis or course of treatment until that surgery is performed."

NBC originally issued a statement attributing the production delay to a "medical evaluation" Tierney was undergoing. The network's choice of words, however, "unfortunately caused some confusion and undue alarm about my health," Tierney said. That's why she came forward with her own clarification.

Parenthood, originally slotted for a fall launch, now will premiere at midseason, once Tierney's surgery and recovery is over.

"My doctors have all assured me this is a very treatable condition," Tierney said in her statement. "I'm very optimistic as to the outcome and want to thank everyone who has sent positive thoughts and support. I look forward to going back to work soon."