Christina Applegate is in good spirits after being treated for breast cancer.

The " Samantha Who?" star had a double mastectomy three weeks ago even though cancer was only detected in one of her breasts, she revealed on "Good Morning America" Tuesday.

Since Applegate has the breast cancer gene, BRCA1, and her mother, Nancy Priddy, had recurring breast cancer, the actress felt she should not leave it up to chance.

"My decision, after looking at all the treatment plans that were possibilities for me, the only one that seemed the most logical and the one that was going to work for me was to have a bilateral mastectomy," she said. "So basically I had a prophylactic double mastectomies."

So now, Applegate is "Absolutely 100-percent clear and clean" and will undergo reconstructive surgery over the next eight months.

"I'm gonna have cute boobs till I'm 90," she joked.

Applegate, 36, will return to the set of "Samantha Who?" when the sitcom resumes filming in September.