The office messages are coming more frequently and they all ask the same question. ‘Dr. Weinstein, my mammogram report said my breasts are dense and that it could miss cancer. The staff where I had my mammogram said I should talk to my doctor about additional testing’.
Prior to this year, the results of a mammogram read in Texas was straightforward and placed into 6 categories designated by the Breast Imaging-Reporting and Data System (BI-RADS).
|Category||Diagnosis||Number or Criteria|
|0||Incomplete||Your mammogram or ultrasound didn’t give the radiologist enough information to make a clear diagnosis; follow-up imaging is necessary|
|1||Negative||There is nothing to comment on; routine screening recommended|
|2||Benign||A definite benign finding; routine screening recommended|
|3||Probably Benign||Findings that have a high probability of being benign (>98%); six-month short interval follow-up|
|4||Suspicious Abnormality||Not characteristic of breast cancer, but reasonable probability of being malignant (3 to 94%); biopsy should be considered|
|5||Highly Suspicious of Malignancy||Lesion that has a high probability of being malignant (>= 95%); take appropriate action|
|6||Known Biopsy Proven Malignancy||Lesions known to be malignant that are being imaged prior to definitive treatment; assure that treatment is completed|
In late 2011, a new variable entered into the equation when the Texas legislature passed House Bill 2102 requiring that mammography providers (usually radiologists) notify all women with dense breast tissue that their results are not as accurate as those of women with less dense breasts. Simply speaking, denser breast tissue means you have a higher chance that cancer will be missed by mammography. It does not mean you have a higher chance of dying from breast cancer. Unfortunately the new mammography law did not provide any guidelines for primary care doctors to use if your breasts are dense.
The American College of Radiology has a system to grade breast composition; often this will be shown on your mammogram report. We have long known fatty breast tissue is easier to see through than glandular tissue and as women age their tissue becomes fattier. The grading system is as follows:
Grade 1. The breast is almost entirely fat (less than 25% glandular)
Grade 2. There are scattered fibroglandular densities (approximately 25% – 50% glandular)
Grade 3. The breast tissue is heterogeneously dense, which could obscure detection of small masses (approximately 51% – 75% glandular)
Grade 4. The breast tissue is extremely dense. This may lower the sensitivity of mammography (greater than 75% glandular)
The findings on a mammogram of grade 3 or 4 will be reported as dense breasts. Dense breasts mean you have less fatty tissue, from a cosmetic standpoint that is a finding most patients are probably happy about. The issue with dense breasts is they can sometimes obscure a tumor.
There are two alternative ways to examine the breast for cancer. Breast ultrasound can pick up larger masses although it will have a tendency to miss smaller cancers. Breast MRI (magnetic resonance imaging) on the other hand is very sensitive for picking up potential abnormalities. Unfortunately it will often detect tissue abnormalities that are truly not a malignancy. This can result in unnecessary anxiety along with unnecessary biopsies for the patient. You should always asked to be referred to a radiology group that focuses on breast disease, as they will have the most experience in reading studies.
So how do you decide if you need further evaluation after your mammogram reveals dense breasts? I like to sit down with the patient review their history and use the National Cancer Institute Breast Cancer Assessment Tool to provide patients with objective data regarding their risk for breast cancer compared to the general population. There is no set pathway to follow for a mammogram showing dense breasts. How to proceed is a decision made after being educated about the risks and benefits.
We still do not have a great test to detect early breast cancer. The best thing you as a patient can do is get your yearly digital mammogram after age 40 or 10 years before the youngest family member diagnosed with breast cancer. Continue with your yearly clinical breast exam with your doctor and perform monthly self-breast examination after your cycle is complete or for those no longer having a cycle, the same time every month (i.e. the first of each month).
The FDA recently approved a computer assisted breast ultrasound technology that is used in conjunction with a digital mammogram. Hopefully this technology will become available to women in this area in the next year.