08/18/2008 AT 08:00 PM EDT
Christina Applegate says she's now free of breast cancer following treatment.
"I'm clear," Applegate, 36, tells Good Morning America
. "Absolutely 100 percent clear and clean. ... They got everything out so I'm definitely not going to die from breast cancer."
In an interview airing Tuesday,
the star of Samantha Who?
, who was diagnosed
a month ago, says the cancer was discovered in the second of two MRI tests done as a follow-up to a biopsy performed last year.
"I was so mad and I – I just remember I was – I was just shaking," she says. "And then also immediately, I had to go into ... 'take-care-of-business-mode,' which was ... I asked them, 'What do I do now? What – what is it that I do? I get a doctor, I get a surgeon, I get an oncologist? What do I do?'"