National report — The female breast contains fewer milk ducts than previously thought, and fatty and glandular breast tissue are all but inseparable, according to authors of two new studies. Both findings have implications, authors say, for breast reduction surgery.
In one study, Australian researchers examined the breasts of 21 lactating women via ultrasound to ascertain factors including the number of milk ducts and ductal morphology, as well as the distribution of glandular and adipose tissue. They found an average of about nine main ducts per breast and cautioned that ablating as few as four of them through breast surgery could "completely impair the subsequent lactation potential of a breast" (Ramsay DT et al. J Anat. 2005 Jun;206(6):525-534).
"The previous major study on the anatomy of the lactating breast was published in 1840. And there haven't been any definitive studies since that time," says Peter E. Hartmann, Ph.D., a study co-author and professor at the school of biomedical and chemical sciences, University of Western Australia.Defining ductal structure
In that study, Sir Astley Cooper injected hot wax into the ducts of cadavers to define the ductal architecture, Dr. Hartmann says.
"It was very good work for its time. But in his studies he said that he saw one woman who had about 20 ducts opening at the nipple. However, he also stated many of those ducts were nonfunctional. Really, he saw around 10 to 12 functional ducts, similar to what we found," he says.
Dr. Hartmann says Dr. Cooper's work has been misinterpreted so that it is widely accepted that the average breast contains 15 to 20 functional ducts.
He says Dr. Cooper additionally noted enlargement of the ducts, which he called lactiferous sinuses, whose purported purpose was to store milk.
"That's been the culture ever since. But one must remember that he actually forced hot wax into the ducts to look at their architecture. So that pressure actually expanded the ducts around the nipple area. Normally, these ducts are not expanded at all, and they don't store milk. They increase in diameter only when milk ejection occurs, for about two minutes, and then contract again" to an average size around 2 mm.
Dr. Hartmann adds, "We see a lot of secretory tissue just underneath the nipple-areola area," while anatomic diagrams commonly show only ductal tissue there.
"What's important for cosmetic surgery is that the fatty tissue and the secretory tissue are within the glandular-to-secretory area. And it's very hard to separate the two; it's not a matter of just making the breast smaller by taking out the fatty tissue, because based on what we see under ultrasound it would be impossible. There are not balloons of secretory tissue around the fatty tissue that are easily dissected away. I hope (these findings) direct plastic surgeons to look at how they do breast reductions in terms of trying to maintain breast function," he says.
A separate study involving histologic sections of freshly preserved breast tissue likewise shows breast fat and glandular tissue to be inseparable, and "present in continuity with each other except in the subcutaneous plane, where only fat is present (Nickell WB, Skelton J. J Hum Lact. 2005 May;21(2):126-130)."
"The emphasis in breast reduction surgery in the last few years has been on the so-called short scar (procedure), totally ignoring the function of the breast. With the short scar, surgeons also usually have a very small pedicle, which means that one is probably going to take away most of the sensation of the nipple and areola. And it's pretty well documented that the ability to lactate is related to sensation in the nipple-areola complex (NAC)," says William B. Nickell, M.D., a board-certified plastic surgeon and general surgeon in private practice in Birmingham, Ala.