Clinical Cases - Pectoral Region & Breast

A 58-year-old woman presents to her physician complaining of rib and back pain following a trip-and-fall accident. She was concerned that she may have broken something. On physical exam, the physician notes some rib tenderness, but also finds a palpable mass in her right breast. The woman says that she does not perform monthly self-exams on her breasts and has not had a breast exam since her last checkup several years ago. A mammogram and rib and spine films were ordered by the physician. The mammogram shows a large mass consistent with cancer in her right breast and the bone films show multiple osseous lesions consistent with metastatic disease.

Questions to consider:

1. Where may breast tissue be found?
   

   Breast tissue may be found anywhere along the mammary or milk line from axilla to groin, but usually in the pectoral region between the clavicle, sternum, costal margin and axilla.

2. Why does the physician order separate breast and bone films?
   

   Both breast and bone films would be ordered since one film will not show both simultaneously due to the differences in density. Since cancer is suspected with the lump in the breast, the film of the bones might show if there are any metastases to them.

3. How can breast cancer spread or metastasize?
   

   Breast cancer can metastasize via the blood or via the lymphatic system.

4. What route did the tumor metastases take to get to the ribs and other bones?
   

   The most likely route for the cancer to reach the bones would be through the intercostal veins, i.e. hematogenous spread.

5. What lymph nodes might show cancer cells in them?
   

   In addition to the bones one would suspect that the axillary lymph nodes, especially the pectoral group might be involved. Parasternal (internal mammary) nodes could be as well.

6. What other organs might be involved?
   

   If the cancerous cells had spread directly via the venous system the next organs in jeopardy would be the lungs, since they are downstream, so to speak, and would be the first capillary bed the cells came to after entering the vascular system. If the tumor cells overwhelmed the axillary lymph nodes, they too ultimately drain into the venous system where lymph enters the venous system at the junction of the internal jugular and subclavian veins.

7. What might be evaluated in determining the prognosis of this patient's disease?
   

   The prognosis would depend upon the extent of the metastases and which organs were involved. This could be assessed by CT scans, nuclear scintigraphy, liver, brain and bone scans, to identify tumors or areas of rapidly dividing cells indicative of cancer metastases.

8. What types of treatment might she expect?
   

   Treatment would be to surgically remove the tumor, breast or some portion of it and perhaps adjacent tissues and axillary lymph nodes. Axillary lymph nodes are not removed to stop the spread, but to stage the cancer. Other treatment would depend upon which if any other organs are involved and might include radiation and/or chemotherapy to kill the tumor cells that have metastasized.

A forty-five-year-old female who recently delivered a healthy infant presents to her primary care physician with complaints of pain when she abducts her right arm. She also reports tenderness around her right axilla and redness around her right nipple. The patient reports she is breast feeding her infant and has also noticed a peculiar drainage from the same breast. The patient also reports that prior to her pregnancy she performed breast self-exams intermittently and noticed no unusual masses or discharges from either breast. On examination, the physician notes that the patient has a reddened area at six o'clock on her right breast. On palpation it is firm, and purulent non-bloody drainage is expressed from the nipple. The physician suspects that it is mastitis and prescribes antibiotics and cessation of breast feeding (while continuing to use a breast pump).

Questions to consider:

1. What groups of lymph nodes filter the lymphatic drainage of the breast and could help prevent or slow down the spread of infectious material?
   

   Pectoral (anterior axillary) nodes
   Central axillary nodes
   Apical/subclavian nodes
   Parasternal (internal thoracic nodes)

2. Which lymph nodes receive most of the lymphatic drainage of the breast? Where will the lymphatics from the nipple drain?
   

   Pectoral and central axillary lymph nodes receive the bulk (75%) of the lymphatic drainage. The anterior intercostal region drains medial toward the parasternal/internal thoracic nodes and the superior portion of the chest wall drains toward the subclavian nodes. More superficial regions of the breast drain along the subcutaneous lymphatics to the contralateral breast and superior abdominal wall. Most of the lymphatics from the nipple, areola, and lobules of the breast will drain to the subareolar plexus. This plexus then meshes with a larger cutaneous circumareolar plexus through which lymphatics may travel to the opposite side of the chest wall.
   
   The major pathway of lymphatic drainage from the mammary gland is along lymphatic channels which parallel:

   1. subcutaneous venous networks to the contralateral breast and to the abdominal wall.
   2. tributaries of the axillary vessels to the axillary nodes.
   3. tributaries of the intercostal vessels to the parasternal nodes and posterior mediastinal nodes.
   4. tributaries of the internal thoracic (mammary) vessels to the parasternal nodes.
   5. tributaries of the thoracoacromial vessels to the apical nodes.

3. What is the origin and insertion of the following muscles and how are they related to the breast?
   

   Pectoralis major:
   
   Origin: Sternal half of the clavicle and the lateral anterior surface of the sternum and manubrium to the seventh rib.
   
   Insertion: Distal fibers from a thick tendon that inserts on the lateral lip of the intertubercular groove of the humerus (aka. crest of the greater tubercle).
   
   Pectoralis minor:
   
   Origin: Third, fourth, and fifth ribs and the aponeurosis of the external intercostal muscles.
   
   Insertion: Coracoid process of the scapula.

4. What nerves provide sensory innervation to the breast? Why has the patient been feeling pain in the nipple and what nerve is involved?
   

   Sensory innervation is provided by lateral and anterior cutaneous branches of intercostal nerves 2 through 6. The pain in the nipple is conveyed by the anterior cutaneous branch of the 4th intercostal nerve which extends midline to the nipple.

5. Why does the patient have pain during abduction? What nerves innervate pectoralis major and minor muscles?
   

   The patient's pain and difficulty in raising her arm might be related to inflammation of the nerves which supply her pectoralis major muscle. These nerves would include both the medial and lateral pectoral nerves, which are branches of the brachial plexus.

6. The following nerves are related to the axillary lymph nodes and to the breast; match the following nerve with the appropriate muscle:

   Long thoracic nerve - Serratus anterior
   Thoracodorsal nerve - Latissimus dorsi
   Medial pectoral nerve - Pectoralis minor and sternocostal portion of major
   Lateral pectoral nerves - Pectoralis major, clavicular head

7. What are the major arteries and veins of the right breast?
   

   Arterial: The arterial blood supply is from several sources. Anterior perforating branches of the internal thoracic artery pierce the second through the fifth intercostal spaces. Branches of the axillary artery include the lateral thoracic artery and thoracoacromial arteries. Finally, there are lateral cutaneous branches from the posterior intercostal arteries.
   
   Venous: Venous drainage occurs from the breast primarily through tributaries to the axillary vein. Additional venous drainage occurs via the internal thoracic, lateral thoracic, and the intercostal veins (third through the fifth).

8. This patient has a subareolar abscess of the breast. Mastitis usually occurs during lactation and breast feeding, and is typically caused by the organism Staphylococcus aureus. Treatment of this patient would include antibiotics, incision and drainage of the abscess and excision of the diseased duct . Due to the patient's age, a careful follow-up should be performed in order to rule out an inflammatory carcinoma. Questions to ask the patient with regard to the nature of nipple discharge would include: Is the discharge uni- or bilateral? Is it milky? Is it blood tinged? Blood tinged discharge from one breast could be suggestive of an underlying malignancy - the most common of which would be an intraductal neoplasm.
   

References:

Clinically Oriented Anatomy (1992): pp 44-48.
Pre-test Self-Assessment and Review (1991) : pp. 87
Gross Anatomy Quizmaster (1996): Quiz 4
Advanced Surgical Recall (1994) pp. 515 -517.
Moore's Clinical Anatomy pp. 72 - 74.
Burkel, et al. pp. 107 - 114.