New guidelines saying women between the ages of 40 and 50 should not receive mammograms to screen for breast cancer have met a groundswell of rejection from many medical centers, breast cancer survivors and numerous doctors -- some of whom have advised their patients to ignore the recommendation.

The American Cancer Society and the American College of Obstetrics and Gynecology are among the many groups that supported the old guidelines and have stood firmly by them since the United States Preventive Services Task Force released its new recommendations Monday evening.

The USPSTF, a panel of independent medical experts, said it was recommending against annual mammograms for women between the ages of 40 and 49, saying the risks outweighed the benefits from earlier screening. That announcement, which goes against a trend of recommending increased screening by cancer agencies, has left many confused.

Meanwhile, doctors' offices and hospitals have been fielding calls from women wanting to know what these new guidelines will mean for them.

One of these calls came not from a woman concerned about getting breast cancer but one who has already had it. Beth Thompson, 44, a mother of four who lives in the suburbs of Baltimore, Md., was first diagnosed with breast cancer following a mammogram at the age of 40.

"I had no risk factors and no family history," Thompson told ABCNews.com. "Under the new guidelines I wouldn't be screened. That's why I'm so upset about this. I firmly believe I would not be here today if I had not had a screening mammogram at 40."