Do you know the No. 1 cause of medical malpractice suits in the U.S. today? It's when a diagnostic reading of a mammogram for possible breast cancer takes too long.

Understandably, women can get antsy while waiting to know what's what--and this anxiety on our part makes some radiologists over-cautious (and so take more time) when reading the mammogram and making the diagnosis. It's a vicious circle.

We breast cancer experts, however, have been worried for some time now about how screening mammograms are being read in this country. Now a study in the Journal of the National Cancer Institute has analyzed data from a great many diagnostic-mammogram interpretations and the results are surprising.

First, let's start by identifying the two types of mammograms. The screening mammogram is your annual mammogram: No lumps, bumps, or troubles that you are aware of. A diagnostic mammogram is done when some problem has been found, either by a breast self exam, by your doctor on clinical breast exam, or by a screening mammogram that has spotted an abnormality but needs more information to determine the cause.

The JNCI study focused only on interpretations of diagnostic mammograms and--perhaps not surprisingly--found that radiologists' diagnostic interpretations vary significantly between mammography facilities. Data were analyzed from over 28,000 diagnostic mammograms read by 118 radiologists. The researchers also assessed whether certain characteristics of the mammogram facility might be linked to how that facility went about interpreting its diagnostic mammograms.

After adjusting for certain characteristics of both the patients and the radiologists, the scientists found that the numbers of false-positive readings varied significantly between facilities.

And the important find was that false-positive rates were significantly higher at those facilities that had previously reported increased concern about malpractice suits.

What do a particular radiologist's fears about malpractice suits mean for you, the patient? Possibly more biopsies, certainly more imaging studies, and probably lots of sleepless nights, as your overly cautious doctor draws out the diagnosis for weeks and weeks, "just to be sure."

When you think about it, though, it makes perfect sense for radiologists to over-report rather than under-report the presence of cancer until it's proven otherwise.

What can you do to reduce the chances that a false positive will happen to you?

• Be sure to have your mammograms read by a radiologist who specializes only in interpreting images of the breast.
• Conversely, avoid the general radiologist who reads a few random mammograms each day or week.