"Through my attempt to get pregnant for the third time through [in vitro fertilization], I sadly found out that I have the early stages of breast cancer," the Giuliana & Bill star told Ann Curry during a Monday morning appearance on NBC's Today show.
"It's been a shock because I recently found this out, and a lot of people have been asking, 'We saw in the season finale of your show that you went and got IVF, so what happened? Are you pregnant?' But sadly, we've had to put that off because of the news."
Rancic explained she discovered she has breast cancer after she got a mammogram when her IVF doctor demanded -- over her objections -- she do so before beginning her third attempt at fertility treatment.
"When we went to do the third round of IVF, this doctor -- the only doctor who's ever said this to me -- said, 'You need a mammogram.' And I said, 'Why? I'm only 36-years-old, so why would I need a mammogram? I'm too young.' And he said, 'I don't care if you're 26, 36. I will not get you pregnant if possibly there's a small risk that you have cancer, because if you get pregnant, it can accelerate the cancer -- all the hormones will accelerate the cancer,'" Rancic told Curry.
"And so I went and got a mammogram. I wasn't prepared to get a mammogram until I was 40-years-old, like I've been told. So I never, in my wildest dreams, expected anything would be wrong. I did go kicking and screaming to get a mammogram, to be honest. But I went, and they called me the next day and said, 'We need you to come back. We see something.' I remember where I was when I heard that. I was driving to work and it was just a kick in the stomach and I knew something was wrong."
Rancic -- who is married to the original The Apprentice winner Bill Rancic -- said that she plans resume her IVF attempt to get pregnant after her cancer treatments are over.
"I'm doing surgery this coming week and then I go to radiation for six-and-a-half weeks... I'm not going to give up. I want that baby," the reality TV star added.