E! News host Giuliana Rancic announced yesterday that she has early stage breast cancer . . . and she's only 36.

She made the announcement on the "Today" show, saying the cancer was caught back in August while she was preparing to try to get pregnant through in vitro fertilization.

Her doctor insisted she get a mammogram as a precaution because pregnancy hormones could accelerate cancer . . . if she had it.

She said, quote, "I wasn't prepared to get a mammogram until I was 40 years old. I never in my wildest dreams expected anything to be wrong."

But she added, quote, "I will be okay, because I found it early. I'm doing surgery this coming week, and then I go to radiation for six and a half weeks."

Giuliana . . . who's married to the very first "Apprentice" winner Bill Rancic . . . also said she still plans to have a baby . . . and even though it hasn't even been conceived yet, she says that baby has already SAVED HER LIFE.