Wellend Health

Women's HealthEducation Center


Is Breast Density Normal?

17 May 2017 | By Wellend

Very dense breast tissue is normal in women who are pregnant and breastfeeding.  But is it normal for everyone else?  

The reason why we are asking this question is because we evaluated 73 well-recognised English speaking cancer organisations for their message regarding breast density using the qualitative data analysis software, ATLAS.ti®.  The concept of HMBD being normal was analysed for rich and thick narrative implication.

The results?

54 organisations used rich and thick narrative to imply that HMBD wanormal.
19 organisations did not mention HMBD.
0 organisations implied that HMBD was not normal.

The word normal, when used by health professionals has two meanings.  First, it means ideal, perfect, or healthy.  Second, it means within the average, or the middle of a distribution, for a population group.1

Using this 2 part definition, is breast density normal?

There is significant evidence that high mammographic breast density (HMBD) increases the risk of developing breast cancer 2 and increasing evidence that cells in dense tissue are abnormal.3  Therefore, HMBD is not normal (ie healthy) because it is not an ideal or healthy condition.

As an example, Figure 1 demonstrates the abnormality of the breast tissue in a 75-year-old woman with a high volumetric breast density of 25% and an invasive breast carcinoma.  Dr Birrell performed the surgery to remove the tumour.

This tissue doesn’t feel normal. The extreme elasticity of the tissue makes it feel like the inside of a golf ball rather than like the soft fluidity of breast tissue that has a lower fibroglandular to fat ratio. It is so tough that it can’t be cut with scissors, rather a scalpel or special knife has to be used.

Dr Steve Birrell
30-year veteran breast cancer surgeon


Is HMBD normal because it is so common?  It is estimated that approximately 40% of Caucasian women aged 40 to 65 have HMBD.  But can we call that normal (ie common) when we don’t know how long this condition has been so prevalent?

In response to this question, Wellend Health submitted an abstract to the 8th International Breast Density and Cancer Risk Assessment Workshop held in San Fransico CA in June 2017.  Our position is no.  One cannot claim that HMBD is normal because it is impossible to determine if HMBD has always been so prevalent in women of this age group.

By applying Ockham’s Razor, the hypothesis that HMBD is normal (ie common) must be rejected as it cannot be proven.  It is not possible to say what mammographic density was 40 years ago, much less 400 or 4000 years; therefore, the hypothesis “HMBD is normal” cannot be proven. (See Figure 1)



So what’s the big deal with “normal”?


If a condition is deemed ‘normal,’ then it is not likely that preventative or therapeutic interventions to correct the condition will be developed.

In 19XX, it was discovered that having high cholesterol increases one’s risk of heart disease.  Because high cholesterol was so common in the American population (where this connection was discovered) that the condition was considered ‘normal.’  It took another 70 years before the first therapeutic intervention was introduced.

Now, over 50% of the population over the age of 50 is taking a cholesterol lowering medication.  There is no doubt that this medication is reducing the incidence of heart disease.

Wouldn’t it be great if the incidence of breast cancer started to go down instead of up!

With HMBD, it has been shown that if it can be reduced then the risk of developing breast cancer is greatly reduced.4  (10% reduction = 64% reduction in risk) There are also strategies that one can consider to prevent HMBD from forming in the first place.  But if HMBD is considered normal, will people know to avoid it?

We believe that by changing the public narrative regarding HMBD – that it is not normal, will result in a more rapid development of preventative and therapeutic interventions.



1.  Wellman M. The Concept of Normal in Medicine. Can Med Assoc J. 1958 Jul 1;79(1):43-4

2.  Boyd NF,  et al. Heritability of mammographic density, a risk factor for breast cancer. N Engl J Med. 2002;347(12):886-94.

3. Turashvili G et al Columnar cell lesions, mammographic density and breast cancer risk. Breast  Cancer R es Treat 2009  11   5(3): 561  571.

4. Cuzick J et al. Tamoxifen-induced reduction in mammographic density and breast cancer risk reduction: a nested case-control study. JNCI 2011 May 4;103(9):744-52. doi: 10.1093/jnci/djr079.
Epub 2011 Apr 11.