About the new breast anatomy

The standard model of the breast is largely based on anatomical dissections carried out on cadavers by Sir Astley Cooper and published in 1840 under the title "On the anatomy of the breast". Shockingly enough, until Medela decided to sponsor the research that led to the findings we hope to announce at the RCM conference, his results had never been corroborated by modern investigative methods.

The currently accepted model of the breast is thus over 160 years old. It is based on wax casts and dissections prepared by Cooper, one of which is reproduced below, that introduce several artefacts into the model. Notably, the injection of coloured wax into milk duct openings at the nipple inflated those ducts, giving the impression that near the nipple they expand into milk storage sacs called "lactiferous sinuses". Another example: in order to illustrate the milk ducts, Cooper - who had likened them to the intertwined roots of a tree - laid them out in an ordered manner for the artist to draw. And it is this ordered lay-out that has been copied into anatomy diagrams ever since.

Dr Donna Ramsay and her colleagues, working with a Medela grant under the leadership of Professor Peter Hartmann at the University of Western Australia in Perth, decided to investigate the lactating breast using sophisticated ultrasound technology.

Their findings overthrew a number of commonly accepted conclusions. The new picture of the anatomy of the breast they revealed will change the way the breast is cared for, especially during surgery.

The changes identified in the diagram below are:

• Ducts branch closer to the nipple
• The conventionally described lactiferous sinuses do not exist
• Glandular tissue is found closer to the nipple
• Subcutaneous fat is minimal at the base of the nipple

Other novel insights not identified in the diagram include the following:

• The external shape or size of the breast is not predictive of its internal anatomy nor of its lactation potential
• The ratio of glandular to fat tissue rises to 2:1 in the lactating breast, compared to a 1:1 ratio in nonlactating women.
• 65% of the glandular tissue is located within 30 mm from the base of the nipple
• Between 4 and 18 milk ducts are exiting the nipple (textbooks such as Gray’s Anatomy talk of between 15 and 20 lobes and milk ducts per breast)
• The network of milk ducts is complex, not homogenous. It is not always arranged symmetrically, nor in a radial pattern.
• The milk ducts near the nipple do not act as reservoirs for milk

The implications for breast surgery are clear. Since the number of milk ducts in the breast is lower than previously believed, the loss of only a few ducts can seriously compromise a woman’s ability to lactate.

Some other examples: in the old model, fatty tissue is undifferentiated. The reality, as Dr Ramsay shows, is that there are three clearly defined areas of fatty tissue. There’s more glandular tissue than previously believed, too. And it is concentrated near the nipple, not evenly distributed in the breast. All these findings and more ill have to influence surgical strategies to ensure women maintain their ability to breastfeed their babies.

The evidence shows that surgeons working with Cooper’s outdated model inadvertently put the ability of their patients to breastfeed at risk. One study showed that women with previous breast surgery had a greater than three-fold risk of lactation insufficiency when compared to those women without surgery.

Another study found that for women with breast reduction surgery, the median duration of exclusive breastfeeding was 5 days, while it was 3 months for women that had not had surgery .

Similar symptoms arose in women who chose breast augmentation surgery: in one study, 64% of those women had insufficient milk supply .

More and more British women of an increasingly younger age opt to have breast enhancement or reduction surgery. At the same time, the benefits of breastfeeding are ever more evident. That is why it is so important that the renewed breast anatomy receives as much publicity as possible. The breastfeeding potential of the UK’s women must be protected as much as possible.

¹Anatomy of the lactating human breast redefined with ultrasound imaging, D.T. Ramsay et al., J. Anat. 206:525-534
²Neifert, MR et al. (1990) The influence of breast surgery, breast appearance and pregnancy-induced changes on lactation sufficiency as measured by infant weight gain. Birth 17:31-38
³Souto, GC et al. (2003) The impact of breast reduction surgery on breastfeeding. J Hum Lact.19(1):43-49
⁴Hurst, N (1996) Lactation after augmentation mammoplasty. Obstet. Gynecol. 87:30-34

Note: The Department of Health recommends exclusive breastfeeding for the first six months. If you or a friend would like help in coping with any breastfeeding difficulties, please see your midwife or health visitor, or refer to our Support Links.