‘SAMANTHA Who?” star Christina Applegate says “the floodgates just opened” when she met the surgeon who would perform a double mastectomy on her.

Applegate, 36, diagnosed with breast cancer last summer, says on today’s “Oprah” that she didn’t get emotional until meeting with her surgeon.

“You know, I – at first I didn’t [cry],” she says. “And then when I met with my doctor and I told him that was my decision and he brought the surgeon in, it was like the floodgates just opened.

“And I – I lost it,” she says.

“Oprah” airs at 4 p.m. on Ch. 7.