The star of 'Samantha Who?', who was diagnosed a month ago, said that 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 said.
"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?
"They got everything out so I'm definitely not going to die from breast cancer," said Applegate.