The answer to your question isn't straightforward. Most abnormalities found on screening mammograms turn out to be insignificant — in other words, not breast cancer — when additional views are completed.
What's most important is whether the second facility reviewed and compared their images with those from your first mammogram. This is necessary to understand what the original concern was, and to determine if additional imaging may be required.
You may need more mammogram images — sometimes called magnified or compression views — or evaluation with a breast ultrasound. After these additional imaging tests, the radiologist will determine whether a biopsy to remove a sample of tissue for testing is recommended.
It's most helpful for the radiologist who reads the mammograms to have your current mammograms and your past mammograms to assess whether the area of concern is stable or new. This may require the facility you choose to request your previous mammograms from other facilities.
Another important piece of information in the evaluation of an abnormal mammogram is to find out if you have noticed a new change, such as a breast lump or skin changes, or if your doctor has detected an abnormality during a recent clinical breast examination.
If you're still uncomfortable with the radiology report and evaluation, then you may wish to get another opinion at a breast center. A short-term follow-up in six months may be recommended to repeat the breast examination, to assess for stability in the mammogram images and to determine if an additional test, such as a biopsy, is necessary.