Click on the image for the full image.
Slide 1. The milk line develops in the fetus extending from the axilla to
the grain as an epidemically derived structure from the skin. The slide
shows a transverse section with early branching of the major lactiferous
ducts. Epon imbedded toluidine blue staining. 63X
Slide 2. In females a doughnut shaped disk of stroma, into which the branching
duct tree descends, is forming several years before the onset of menses.
This 2mm thick slice of breast shows the blue staining of the epithelium
since nuclei stain with the hematoxylin. Note the early formation of lobules
around one of the ducts and the convergence of the major lactiferous ducts
at the nipple. 1X
Slide 3. As the breast enlarges the dense connective tissue stroma is dispersed
by fat. The c denotes the area magnified 5X in the next slide.
Slide 4. The blue balls are the cellular lobules, the potentially milk microorgans.
They stain blue since hematoxylin stains the nuclei. 3X
Slide 5. Each breast is composed of 6-8 LOBES shaped like pie pieces around
the nipple. Contrast material was injected into one major lactiferous duct
and an x-ray was taken and illustrates the branching duct tree of a single
Slide 6. The major lactiferous ducts converge on the nipple in the slice.
Slide 7. This transverse cut shows some of the 5 lactiferous ducts filled
with secretions. 1.5X
Slide 8. Two major lactiferous ducts are seen longitudinally to descend
several centimeters before any blue lobules are formed. This is indeed nature's
nursing bottle. The area needs to be empty so that the infant can bite down
on the lactiferous ducts while nursing. 1X
Slide 9. This histological section shows the nipple and some areola. Epithelium
stains blue with hematoxylin and stroma stains red with eosin. Note lactiferous
duct at the surface of the nipple. It is plugged with keratin. 1X
Slide 10. At higher magnification the keratin plug is seen better. This
mechanical barrier prevents bacteria from entering the duct in non-lactating
Slide 11. The histologic slide of a major duct is seen in 2 dimensions.
Slide 12. The same duct is seen in 3 dimensions in the breast slice. 6.3X
Slide14. A cluster of TDLU is seen at higher magnification from the previous
slide. Note how the TDLU radiate around the small duct like spokes of a
wheel. That architecture will allow the TDLU to expand in all directions
during physiological hyperplasia of pregnancy and lactation. 3.5X
Slide 15. This diagram shows the branching ducts (D). The extralobuler terminal
duct (ETD). From the intralobular part of the terminal duct (ITD) ductules
(DTL) develop like test tubes as blindly ending structures. 30-50 ductules
are present in each TDLU and can be alikened to the delicate petals of a
Slide 16. The histologic appearance of several TDLU at low magnification.
Slide 17. At higher magnification note the sharp interphase between dense
extralobuler connective tissue and each TDLU. 25X
Slide 18. At even higher magnification the loose intralobular stroma is
noted investing the ductules. 63X
Slide 19. A single ductule cut transversely shows two cell types, an inner
layer of secretory cells with abundant mitochondria and an outer sparse
cell layer of myoepithelium with sparse cytoplasm. Epon imbedded toluidine
blue stained. 250X
Slide 20. A single ductule is shown in this electronmicrograph. Fat droplets
are noted in the apical cytoplasm of the secretory cells adjoining the lumen.
The outer flattened myoepithelium contains abundant cytoplasmic filaments.
The myoepithelium contracts when oxytoxin is released from the posterior
pituitary gland during the early phase of nursing. Thus, the milk in the
lobules is literally squeezed into the duct tree during nursing. This pituitary
hormone is called the let down factor. Prolactin and endorphins are released
into the blood stream from the pituitary by the let down factor stimulation.
The nursing mother is thus experiencing extreme well being and contentment
from her surge of endorphin hormone, the happiness hormone you could call
it. The prolactin ensures nurturing behavior of the offspring and is the
love hormone Nature has devised a pay-off in all facets of reproductive
Slide 21. Each ductule is invested with a basement membrane stained red
with Periodic Acid Schiff (PAS). 100X
Slide 22. Pregnancy hormones induce hyperplasia of TDLU. In this slide from
a 5 months pregnancy the enlarged lobules have crowded out the extralobular
connective tissue. 5X
Slide 23. This histologic slide shows the glandular hyperplasia crowding
out the intralobular stroma. 200X
Slide 24. This "Normal" lobule is from a non-pregnant 49 year
old female with breast cancer. It has the appearance of a younger female.
However, women with breast cancer retain a youthful breast parenchyma.
Slide 25. This normal lobule is from a 43 year old female with no breast
cancer. Note the thickened basement membranes around the ductules. The lobule
is starting to become sclerotic. 63X
Slide 26. This normal lobule displays fewer ductules and denser intralobular
stroma. Non-cancerous breast from an 83 year old female. 63X
Slide 27. In this breast slice the lobules show moderate atrophy. Note the
distended duct tree. From a 59 year old female with no breast cancer. 8X
Slide 28. This breast slice shows complete atrophy of the TDLU but the branching
duct tree will remain forever. From a 52 year old female with no breast
Slide 29. This breast slice shows the branching duct tree distended with
secretion and a few remnants of lobules. The flowing tree of the young breast
has become cacti in the desert. 4X
Slide 30. This breast slice illustrates the branching duct tree and a single
TDLU with a delicate terminal duct. The microarchitecture of TDLU is recapitulated
in pre-cancerous lesions and ductal carcinoma in-situ, as you will see later.
Slide 31. In this slice at 10X the punctate appearance of the lobule is
due to the individual ductules making it possible to discern it as a normal
Slide 32. This slice of breast has been stained supravitally with methylene
blue chloride. They have the same punctuate appearance so the structures
are normal lobules. 6X
Slide 33. Two such lobules have been dissected for experiments. They are