Melisa writes:

<I've been following the conversation on feedArt's comments section.  Some
of the commenters (and my deleted comment) challenged the fact that they
use the concept of lactiferous sinuses as currently valid.  From what I've
learned lactiferous sinuses don't exist.  . . . . . . . . . .I consider myself to be 
student still and would love some clarification regarding this topic.>


Melisa, I commend your desire to understand this controversy better. My curiosity 
has kept me looking up references for a long time. This topic will be addressed in 
depth at the ILCA convention in Orlando this year by Dr. Michael Woolridge. I am 
very interested in hearing his views, which seem to contrast markedly with those 
of others. 


There are many specialty areas interested and expert in the study of the breast. It is 
to our advantage in the lactation community to become at least a little familiar with the 
evidence based conclusions of others who are expert in the anatomical and physiological 
characteristics of the breast during many different conditions at many different stages of life.


The nomenclature of histology (study of tissues under a microscope, specifically to study
breast diseases) has included lactiferous sinuses for many decades because different 
types of breast disease start in specific types of tissues. Therefore it is very important 
that there be specific names for each distinct type of tissue and part in the breast.

(Azzopardi JG, Ahmed A, Millis RR. Nomenclature of the Microanatomy of the Breast: Parts 
Affected in Different Diseases: Normal Structure and Involution, In: Problems in Breast 
Pathology In: Major Problems in Pathology, Vol. 11 in series, Bennington JL, Ed., W. B. 
Saunders Co. Ltd., London, 1979)

        “The nipple region contains the converging segmental ducts, each of these opening into 
an irregular, corrugated space, the lactiferous sinus, which is a characteristic feature of the 
nipple (2 electron microscope figures). Because of its irregular contour in the contracted state, 
the beginner may mistake the lactiferous sinus for a pathological condition. . . . The sinus 
communicates with the surface of the nipple via the collecting duct or galactophore. In its 
proximal portion this duct is lined by epithelium similar to that of the rest of the ductal system, 
but its superficial portion is sealed by keratinizing stratified squamous epithelium continuous with 
the nipple surface. The junction between the glandular and the squamous epithelium is abrupt.”


Embryologists state that lactiferous sinuses are visible under the microscope in breast tissue of girls, 
boys, men and women, with thick elastic tissue surrounding the walls of the sinuses in adult women.
(Montagna W, Macpherson E, Some Neglected Aspects of the Anatomy of Human Breasts, 
Journ Inv Derm, July 1974, Vol 63;1: p. 10-16.)


Many breast surgeons have published pictures of microscopic views of lactiferous sinuses, 
including those in the surgical specimens of menopausal women.
(Haagensen CD, Diseases of the Breast, Third Edition 1986 W.B. Saunders Co: West 
Washington Square, Philadelphia, PA 19105)


An easier to locate reference referring to the resting breast is:
(Rizzato G, Chersovani R, Macorig D, Perrone R, Department of Diagnostic Imaging, General 
Hospital Italy,  Dynamic Breast Anatomy)      http://www.liveto.com/semi/sonic/pdf/se01.pdf

“With a correct examination, the subareolar tissues are usually echogenic, because 
subcutaneous fat is interrupted at this level. Main ducts coming to the nipple may be 
visualized as anechoic bands, with a progressively increasing diameter. The lactiferous 
sinus is the widest portion of normal ducts, up to 3 mm. wide, and is located just behind 
the nipple.” 


I have been thinking about this subject for decades since a few years after I first saw diagrams 
in the old Ross reproduction series and in the Carnation book of uterine and breast 
transparencies when I was a student nurse in the late 1940's. I wondered whether the 
sinuses developed during the first pregnancy or whether they were formed at some time 
in early life, so I gradually began searching in the medical library. I believe Sir Astley Cooper's 
meticulous work, before modern imaging methods were developed, has been greatly 
misunderstood and unceremoniously and rudely made fun of in certain quotes I have heard. 
Subsequent artists continued to embellish diagrams of lactiferous sinuses ad infinitum. 
(I have one old advertising illustration from the Eli Lilly Corporation with line drawings 
showing the breast and its ducts, with a diamond shown in each lactiferous sinus!)


We recognize that many reproductive organs (in both sexes) change shape, size and 
consistency during various stages of reproduction. Why on earth would nature create
these formations in the embryo so that under the microscope both boys and girls have 
them and men as well as women, except that the sinuses of women have a thick elastic 
layer around their walls? Formations named lactiferous sinuses are visible under the 
microscope in breasts of menopausal women as well, so WHY would nature make them 
DISAPPEAR completely (temporarily) during the only physiologically active stage in the 
life of the breasts??? My logic tells me there must be some other explanation(s).

 
My theory is that they exist for at least two reasons. Their shape allows at least a few fat 
globules to be trapped in their folds in the front of the breasts as the ducts relax and change 
their configuration, causing the rest of the milk to redistribute itself to fit the changed shape 
of containing ducts, according to the specifice gravity of the cream and the skim portions. 
A second reason seems to me to be to give babies the advantage of exerting some extra 
hydraulic pressure. 


But then, that would require some compression on the part of the baby's jaw and tongue. It 
has sometimes been strongly "suggested" that there is no such action and that vacuum (negative, 
or below atmospheric pressure) and the let-down reflex are the only forces that remove the milk. 
Then why does tongue-tie cause such problems? I don't think we can have it both ways. 


My personal clinical experience tells me they do exist, being palpable by the third trimester and early 
postpartum, usually about 1-3 cm. back from the base of the nipple, deep under the areola  In most 
of the thousands of mothers to whom I have shown hand expression over at least 5 decades, to me 
they feel like tiny "B-B's" (buckshot) or tiny lumps in cooked pearl tapioca. The fact that they are 
surrounded with thick elastic walls in females gives me the impression that they begin to expand and 
become palpable as they begin to fill with colostrum during lactogenesis I, from mid pregnancy onward, 
with colostrum probably gradually pushed forward by oxytocin during Braxton-Hicks contractions, and 
able to be expressed in most women during late pregnancy. After birth, frequent nursing and/or 
pumping loosens the elastic tissue so that by 4 weeks postpartum (the earliest time at which the 
research you referred to begins) they are different - slightly larger and much softer to palpation 
and probably appearing much thinner on ultrasound imaging. They seem to return to their contracted 
state when the breast involutes after each lactation ceases.


I believe that much of what happens in the breast is still a puzzle. While there is much that we in 
lactation can contribute to the fuller understanding of the breast, there is so much more that our field 
can yet learn (from other fields) about its anatomy and physiology. My newest interest is in trying to 
learn more about the lymphatic system!


K. Jean Cotterman RNC-E, IBCLC
WIC Volunteer LC      Dayton OH  
 

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