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Sentinel Node Biopsy – Breast

by Craig Canby, PhD
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    00:00 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.

    02:06 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.

    02:43 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 procedure. 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.

    03:53 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.

    05:58 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.

    06:14 That brings us to the key take-home messages from this presentation.

    06:19 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.

    07:17 Extra nipples and/or breast tissue may develop anywhere along the milk line.

    07:23 I thank you for joining me on this lecture on “The Breast”.


    About the Lecture

    The lecture Sentinel Node Biopsy – Breast by Craig Canby, PhD is from the course Abdominal Wall.


    Included Quiz Questions

    1. Thoracodorsal nerve
    2. Long thoracic nerve
    3. Intercostobrachial nerve
    4. Medial brachial nerve
    5. Musculocutaneous nerve
    1. Inject a blue dye at tumor site.
    2. Inject a red dye into central nipple zone.
    3. Inject a red dye at upper outer quadrant.
    4. Inject a blue dye on most fatty area of breast.
    5. Inject dye into axillary region.
    1. Long thoracic nerve.
    2. Brachial cutaneous nerve.
    3. Thoracodorsal nerve.
    4. Medial brachial coetaneous nerve.
    5. Short thoracic nerve.
    1. Lymph node has malignant cells.
    2. Lymph node has excess fat.
    3. Lymph node has been damaged.
    4. Lymph node has excess fibers.
    5. Lymph node has mast cells.
    1. Polythelia.
    2. Polymastia.
    3. Amastia.
    4. Athelia.
    5. Poland Syndrome.

    Author of lecture Sentinel Node Biopsy – Breast

     Craig Canby, PhD

    Craig Canby, PhD


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