of the breast.
On the following slide, I'm going to describe
a sentinel node biopsy and why that's important.
It is important, if a woman has breast cancer,
to determine whether or not the cancer cells
from the breast have metastasized. Again,
keep in mind that 75% of the lymph draining
from the breast drains into the axillary nodes
and the most frequent quadrant involved is
the upper lateral quadrant. We're going to
just assume that that is the location of the
breast and that the lymph from that cancer
site will drain into the axillary lymph nodes.
A sentinel node is the node that first receives
the lymph that is draining from the nidus
or the location of that cancer. So, a procedure
that allows the physician to determine whether
or not the cancer has metastasized is a procedure
called a sentinel node biopsy. And we're going
to assume that the cancer was visualized by
mammography in the lateral upper quadrant.
Lymph will then be received from the cancer
in that location by the axillary lymph nodes.
And the first node to receive that lymph from
the cancer is known as a sentinel node.
The procedure involves, in some cases, the
injection of a dye into the site of the tumor.
So, if the tumor is right in through here,
they'll inject a blue dye. They'll do an axillary
dissection to open up the axillary region
to inspect the axillary lymph nodes. And what
they're viewing is they're viewing the first
lymph node to receive that blue dye. That
will be your sentinel lymph node.
That node is then removed for histologic or
pathologic examination. If that node harbors
metastatic breast cancer cells, then a axillary
dissection of lymph nodes will be necessary,
so they'll all be removed. That usually causes
some complications with the return of lymph
from the affected upper limb. If this was
occurring in the right breast, as the example
that I just provided you was, then you could
have swelling of the right upper extremity.
However, if that sentinel node was examined
histologically and no metastatic cells were
observed, then metastasis had not traveled
to those nodes and this type of axillary node
dissection would be unnecessary. So, this
would then spare the woman from that surgical
If it is determined that a woman with breast
cancer does need a mastectomy, there are some
nerves that are vulnerable to injury during
this surgical removal of the breast. So, these
nerves would have to be clearly identified
and protected. But, some of the nerves that
are vulnerable would include your long thoracic
nerve, your thoracodorsal nerve, your intercostobrachial
nerve, the medial brachial cutaneous nerve
and the medial pectoral nerve.
The first three nerves are visualized or illustrated
on this slide. If we take a look here, we're
looking at the long thoracic nerve. It is
running along the lateral thoracic wall and
it's going to innervate your serratus anterior.
If this nerve is damaged and there's paralysis
of the serratus anterior, the woman will have
a winging of the scapula.
Another nerve that's vulnerable and illustrated
here is traveling with your thoracodorsal
vessels, artery and vein. That is thoracodorsal
nerve. It's innervating your latissimus dorsi.
The third and final nerve that's well demonstrated
here is this nerve that's leaving the second
intercostal space. This is the intercostal
brachial nerve. It's a cutaneous nerve supplying
skin on the arm. We also have the medial brachial
cutaneous nerve that supplies skin on the
arm and then the medial pectoral nerve is
a nerve that will innervate your pectoralis
minor and provide for partial innervation
of the pectoralis major.
This slide depicts the two milk lines. We
have a milk line on the right and then we
have a milk line on the left. These milk lines
are developmental lines or the maturation
of breast tissue during development. All mammals
have them. The molecular signals that are
involved in humans will dictate the location
at which the breast should develop and this
is a normal developmental stage that we see
here. But, you see all these other dots up
and down the milk line on either side. All
these areas along the milk line can produce
extra nipples which is also referred to as
polythelia. You can also have the development
anywhere along the milk line of additional
breast tissue which is polymastia. And you
can also have no development of breast tissue.
In that case, the condition would be amastia.
That could be unilateral, just on one side,
or that could be bilateral, a bilateral absence
of breast tissue.
That brings us to the key take-home messages
from this presentation.
First, the breast overlies ribs 2 through
6 and commonly extends into the axilla as
the axillary tail of Spence.
The areola is pigmented, harbors sebaceous
glands and surrounds the nipple.
The breast contains variable amounts of adipose,
fibrous connective tissue and glandular tissue.
Vessels and nerves of the thoracic wall supply
and drain the breast.
Axillary lymph nodes receive 75% of the lymph
draining from the breast.
The most frequent site of breast cancer is
the upper lateral quadrant.
Sentinel node biopsies inform if a complete
axillary node dissection is required.
Thoracic wall nerves may be injured during
a mastectomy. It must be identified and protected
during this procedure.
Extra nipples and/or breast tissue may develop
anywhere along the milk line.
I thank you for joining me on this lecture
on “The Breast”.