"I don't know if we know that's going to cause harm or not," he said. "What I'm worried about the most, however, is confusion on the part of women and their physicians that may make them question whether mammograms will do anything."
His concerns were borne out in at least one New York hospital on Tuesday.
"I spoke to our breast imaging department today and they said that the 'no-show' rate doubled today," said Dr. Susan K. Boolbol, the Chief of Breast Surgery at Beth Israel Medical Center in New York. "That means that twice as many patients today decided not to show for their mammogram appointment. That is a very concerning rate. We will monitor this to see if it continues."
But Boolbol said she is also concerned that "controversies such as these really create a feeling of mistrust for the medical community at large."
Lyman said the benefits of mammography have been clear, particularly since insurers and Medicare began reimbursing for them, noting that mortality rates have fallen by 25 percent since then.
"I can't say all that's due to mammography, but it's pretty clear that part of that and maybe most of that is due to early detection with routine mammographic screening," he said.
But he agrees with Boolbol about the potential for mistrust, noting that screening rates have fallen in the past few years.
"I'm concerned again, with all this confusion, that women may stop getting their mammograms regularly. We may not know the effect of that [in terms of mortality] for another 10 to 15 years," Lyman said.
While many have said the new recommendations are part of a bid to lower medical costs, Lyman said he does not believe there was an economic motive.
Instead, he said, the issue could be that the panel does not include a breast cancer specialist.
"There's no breast cancer expertise on that panel, and I think it's hard to develop guidelines with the data as it is without understanding breast cancer," he said. "It's certainly not a change in the evidence. Something else is at work."
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."
Thompson explained that in removing the tumor detected by the mammogram, doctors found a faster-growing one underneath, one that would not have been found until it became a palpable lump.
"It really makes me shudder to think of what a different situation I would have been in if that were the case," she said, explaining that she needed four surgeries, four rounds of chemotherapy and took Herceptin, an adjuvant for an aggressive form of breast cancer, for a year.
"That's the treatment that I needed even for an early-stage cancer," Thompson said. "There's just no reason that I would have been screened and no way that it would have been found at the time, except for mammography."