You are here

Research Worth Watching: If We Knew the Anatomy of the Breast

A new analysis by the Agency for Healthcare Research and Quality shows that from 2005 to 2013, the overall rate of mastectomies, combining single and double mastectomies, jumped 36 percent – yet there was no change in the rate of breast cancer diagnoses.

There were 66 mastectomies per 100,000 women in 2005; in 2013 there were 90 per 100,000 women. This increase was driven in part by women choosing double mastectomies, which accounted for 33 percent of all mastectomies in 2013. In 2005, nine out of 100,000 women had double mastectomies. In 2013, 30 out of 100,000 did.

There are many reasons why more women are choosing single or double mastectomies, ranging from fear of a second cancer to a desire for symmetry. It seems to me that the increase in the number of women making this choice is a direct reflection of the failure of the breast cancer research field to define the actual anatomy of the female breast.

Yes, we understand the basic anatomy. There are two breasts that sit on the chest wall. What I’m talking about is the anatomy of the breast ducts. Evidence shows that breast cancer starts somewhere in the breast ducts. Laboratory studies have found that in rodents (mice and rats) breast cancer starts at the junction of the ducts and lobules. But rodents have only one duct per teat, whereas women have six to eight openings in each nipple. This would suggest that women have between six and eight breast ducts in each breast. But because we do not yet have an accurate map of what the breast ducts look like inside the human breast, we don’t know for sure. Instead, we use concepts like quadrants to refer to the human breast. Yet there is no data to support the idea that the ducts are nicely organized into four separate quarters, like the face of a clock.

In the 1980, S.R. Wellings first demonstrated that breast cancers start in the terminal duct lobular unit. If you imagine a breast duct looking like the main branch of a tree and the lobules looking like the leaves at the tips of the smaller branches, the weak point, where cancer would begin, would be where the leaf connects to the branch.

Tibor Tot, a breast pathologist in Sweden who has also been a speaker at the Foundation’s International Symposium on the Breast, thinks of breast cancer in terms of a sick lobe or a sick duct, rather than as something that affects the whole breast. If he is correct, then it would be much easier to find and treat breast cancer. If you could find the sick duct or lobe, you could use surgery to remove it. Or maybe you could even squirt something into it to clean it out, much as you would clean out a clogged drain with Drano®.

The anatomy of the liver, the lung, and the pancreas is clearly understood, and image-guided surgery is commonly used for cancers in these organs. If we had a map of the breast ducts, we would have more options. But without that map, we basically have two choices: breast conservation surgery (lumpectomy) or mastectomy.

And because we can’t tell a woman whether we’ve removed the entire sick duct, we can’t reassure her that her risk of recurrence is low. No wonder we are doing so many mastectomies and preventative mastectomies! How different might things be if we could tell a woman we could remove or treat a sick duct, and she’d be able to keep her breast!

At Dr. Susan Love Research Foundation, we are conducting a study to map the breast ducts in women. Breast ducts aren’t normally visible on a mammogram, ultrasound, or MRI, so we need a way to highlight them. We turned to lactating women, who have naturally occurring liquid (breast milk) in their ducts, and we are using automated whole-breast 3D ultrasound to create images of the ducts in these women. Thanks to our wonderful lactating volunteers, we have done some initial studies. Already, we’ve learned that breast ducts are not equally distributed in a radial fashion, as is often depicted in what I call the pizza image. Even more interestingly, our data shows that there seem to be more ducts in the lower outer part of the breast than in the upper part, where cancer is more common. This data is very preliminary, but it is incredibly intriguing, and we have applied to the National Institutes of Health for a grant to pursue it further.

If we had a good map of the breast ducts that we could use to tell us which tissue should be removed in a woman with breast cancer or in a woman who is at high risk, then I’d venture to guess that some of the women choosing mastectomies might feel comfortable with the idea of keeping their breast or breasts. Until that map exists, we will be hard-pressed to provide them with the information they need to make different choices.