"I was so, so scared of going to the doctor," Tierney tells Parade of the day she found a lump in her breast. "I felt something, and my boyfriend at the time made me go. He said, 'You've got to take care of this,' because I was afraid. That's one thing I will say: Don't be afraid to go to the damn doctor. Just go!"
The diagnosis of breast cancer came in June 2009, requiring the actress to drop out of NBC's then-new show Parenthood. But even then, she said, she never had a "why me" moment.
"I was so lucky," she says. "I had insurance, I found a great team of doctors at UCLA, and I could afford not to work while I was getting treated. From the beginning my doctor told me, 'You're going to be okay,' and I chose to believe him. So there was always that in my head."
That doesn't mean it wasn't an incredibly difficult journey – especially when she got still more bad news.
"It turned out to be a more aggressive kind of cancer than they thought," she explains, adding that her doctor informed her that a decade ago pathologists might have missed it altogether. "He said they would have patted me on the head and told me, 'You're cured,' and I would have died of breast cancer."
Next up for Tierney, 45, who is still in treatment, is a role as a prosecutor on ABC legal drama The Whole Truth.
"There is one thing I've learned for sure," she says. "It's a life-changing thing to be in a position of needing help and being so lucky as to get it. And to feel like that's okay. You can't just take care of everybody else all the time. That's almost as perspective-changing as the illness. For someone like me, that was kind of tough."