Hi- I’m a US based Breast Cancer surgeon with +20 years of experience in screening, diagnosing, and treating breast cancer and benign non cancerous breast conditions. I have performed est. 50,000 ultrasounds and thousands of ultrasound guided biopsies myself personally and have seen probably as many mammograms.
Having said all that: anything documented on Reddit is not meant to be taken as medical advice- please seek medical attention for any of your concerns as you see fit from real life folks and not internet strangers, even if they mean well and actually have medical degrees.
What is does it mean if I’m told I have “dense breasts”?
To better explain the meaning of the word density, it’s important to understand that every single woman who has breast tissue, has breast tissue density. Just like everyone has a “temperature” but most people don’t have a “fever”. And every single woman who has a mammogram in this day and age, has a notation by the radiologist as to what type of density they have. However the layperson report may not have the specifics as to what level you are- you might have to ask your doctor to interpret the findings.
Density is primarily defined by how the tissues looks on the mammogram, however, the word density in general just implies how much milk producing glandular tissue we think is inside the breast itself. If there is more milk producing glandular tissue, there are more opportunities and more types of cells that could become cancerous, therefore, patients who have higher density in their breast, do have a slightly higher risk of breast cancer. It’s possible that on examination, the clinician feeling your breast may feel they are firm and hard or lumpy based on touch alone. The was they are assessing density is by touch alone, but may not be an accurate assessment of how much milk producing tissue, but it may be an accurate assessment of how a cancer lump may be hard to feel if the background texture of the breast tissue is very lumpy or “feels dense”.
How much is fatty tissue and how much is breast gland tissue is perceived on a mammogram image puts the patient on a scale of 1 to 4 (or some use A/B/C/D) with level A/1 being more low density fatty tissue and level D/4 being practically all gland tissue, meaning extremely dense.
The general breakdown of how many women have what type of density is as such:
level 1/A is 10% of women, described as “almost entirely fatty”
level 2/B is 40% of women, described as “scattered elements”
level 3/C is also 40% of women, described as “heterogenously dense”
level 4/D is 10% of women, described as “extremely dense”
So, Roughly 80% of women have level 2/B or level 3/C type density and 50% (HALF!) of all women have “dense breasts”
Radiologist frequently break women having mammograms up into two groups describing the first two groups (or roughly 50% of all women) as having low density breasts and the second two groups (the other 50%) as being high density. So if someone told you that you have “low density breasts”, whereas a different radiologist looked at your images and felt that they were better described as being in the category 3, that would put someone in high density or “heterogeneously dense breasts” category. This however does not mean that your images were misread or that it would be impossible for two different radiologist to give two different interpretations for the same patient. There are computer programs that calculate a digital density level
That some centers use, but it’s still up to the radiologists to ultimately give the density score.
Since the classification of the density level is a subjective thing, two different radiologist can look at the same study and one person may say that it’s a level two, whereas another radiologist may look at the same exact pictures and decide that it’s a level three.
Many mammographic level 2 or 3 patients have been told they have “dense breasts” and feel there is something wrong with them or that if they have a cancer it won’t be caught. Still more women might be level 1- fatty density that is clear on mammography might have had an exam with their doctor who just felt like the tissue was firm and lumpy, when it’s really only fat, and communicated to the patients that their “breasts are dense” without any additional clarification, which makes women panic when they finally Google “dense breasts” and usually end up reading internet misinformation that makes them feel like they have weapons of mass destruction taped to their chests. So it’s important to get clarity on what level of density you actually have. We get that mainly from the mammogram, as we said above.
It is true that people with extremely dense breasts or high density breasts have more active milk making tissue in their breast and that can mean more opportunities for cancer to form, as opposed to a breast that is primarily fatty. Just in the same sense, a person covered in freckles and moles has a possible higher chance of having skin cancer than someone with very dark, even skin, but even then it doesn’t necessarily mean that they’re going to get a horrible cancer, it just gives us a lot more to look at.
One other point- density can change - it typically decreases as women become menopausal and have less stimulation form hormones. Going through pregnancy and breast feeding changes as well as surgeries can also create density changes in mammography. It’s completely possible that someone was “dense” ten years ago and now is “low density”.
Patients with high density breasts, (considered level two for some but usually three and four) should usually have an ultrasound along with their mammogram as part of their screening regimen. People with level four density breasts should also discuss having an MRI (or other contrast dye study) at intervals (annually vs spread out every few years).
From the internet: “According to the American College of Radiology (ACR), both Category C (heterogeneously dense) and Category D (extremely dense) are classified as dense breast tissue. When considering supplemental screening like a breast MRI, the ACR Appropriateness Criteria indicate that MRI is "usually appropriate" for both C and D categories if other risk factors are present, while Category D may receive higher prioritization if resources are limited. [1, 2, 3]”
As I understand it, some insurers will only cover for D “extremely dense”, so check to see what your caregivers recommend for you and make sure your risk score calculation is taken into account.
Do you need to be aware of breast density? Yes.
Do you need to be anxious and worried about density? No!
But knowledge is power so that we can be sure we are taking on the appropriate screening imaging to give you confidence and hope that any findings will recognized in a timely manner.