Journal_Lymph Nodes in Breast Ultrasound

ask the expert Lymph nodes in breast ultrasound Louise Smalley, AMS, Sydney Breast Clinic, NSW. What is the importance of looking at lymph nodes when performing a breast ultrasound? Introduction Anatomy and physiology Axillary nodes There are 20–40 lymph nodes and multiple The presence of metastases in the Understanding the anatomy and lymphatic vessels interspersed in fatty regional lymph nodes is one of the physiology of the regional lymphatic tissue in the axilla [7]. The axillary nodes most important prognostic indicators system is important as axillary are divided into five groups listed below: of patients with breast cancer [1]. lymphadenopathy can have multiple ƒ Traditionally, axillary node dissection causes. Lymphoma, leukaemia, and The anterior axillary nodes include was performed for staging. However, the pectoral and interpectoral nodes. melanoma can all cause metastases in the last decade, in order to reduce in the axillary lymph nodes, as can Pectoral nodes lie along the course of the lateral thoracic vein and the lower the morbidity associated with axillary cancers of the contralateral breast, dissection, sentinel node biopsy has lung, gastrointestinal tract, thyroid and border of the pectoralis major muscle. The interpectoral or Rotter’s nodes commonly been performed and, only if ovary [1]. (fig 1) lie between pectoralis major the sentinel node(s) shows malignancy and minor muscles along the pectoral does the patient proceed to axillary Benign lymphadenopathy can be branch of the thoracoacromial artery. dissection. Sentinel node mapping uses caused by skin and fingernail infections, radionuclides and/or blue dye to detect breast infection or inflammation, ƒ The lateral axillary nodes are found the first lymph node that drains the site fibrocystic change, recent percutaneous alongside and lateral to the axillary of the cancer. This node is removed biopsy, or surgery [1,3]. Other vein. and assessed histopathologically for diseases that can cause benign ƒ the presence of metastases [1]. More lymphadenopathy include tuberculosis, The posterior axillary or subscapular recently, several studies have been HIV and AIDS, autoimmune diseases nodes lie along the subscapular vessels. carried out to determine the accuracy of such as systemic lupus erythematosus, preoperative ultrasound in the diagnosis rheumatoid arthritis, sarcoidosis and ƒ The central axillary nodes lie along of metastatic disease in lymph nodes [2]. psoriasis [1,4–6]. the medial part of the axillary vessels When an abnormal node is identified embedded in the fat of the axilla. They with ultrasound, a percutaneous biopsy Lymphatic drainage of the breast can be performed. If the biopsied node The major portion of the lymph from is positive for metastases, the woman the breast drains to the axillary lymph can proceed directly to axillary node nodes. There are other routes of flow. dissection, negating the need for a The medial portions of the breast drain Pec Major sentinel node biopsy [1–3]. into the internal mammary nodes in the parasternal region. A small amount With the high resolution ultrasound of flow crosses to the other breast and equipment used today, normal lymph axilla and some passes to the upper nodes are readily identified during an abdominal lymph nodes [7]. `Pec Minor ultrasound examination of the breast. It is important for the sonographer to As well as draining lymph from the breast, the axillary nodes also drain 140 be able to differentiate between the lymph nodes that have normal features, lymph from the upper limb; and the 15 fps benign pathology or features suspicious anterior, posterior and lateral walls of the for metastatic disease in order to avoid trunk above the umbilicus including the Fig 1. Rotter’s node seen in a patient with a unnecessary biopsies. back of the neck [7]. large breast abscess. O 16 soundeffects Lymph nodes in breast ultrasound ask the expert are superficial and usually the largest of Lymphatic tissue contained in lymph As the lymph flows through the node, the the axillary nodes. nodes is responsible for the destruction reticular fibres in the lymph nodes impede ƒ The apical or subclavicular nodes are of these microbes and removal of foreign the passage of microbes and other found in the apex of the axilla medial to particles from the lymph fluid [5]. particles. Lymphocytes and macrophages the axillary vein [7]. recognise the foreign particles, microbes Lymph nodes are reniform, or coffee and cancer cells. Macrophages destroy For surgical purposes the axillary bean shaped structures located along some foreign particles by phagocytosis. lymph nodes are also divided into the course of the lymphatic vessels. T cells destroy the foreign cells by levels according to their relationship to The lymph node has a capsule of causing them to rupture or by releasing pectoralis minor muscle as follows: dense connective tissue that extends cytotoxic substances. B cells differentiate Level I – low axillary nodes lying into the node. These extensions, into plasma cells that secrete antibodies. called trabeculae, divide the node into Plasma cells and T cells that have lateral to the pectoralis minor muscle including the lateral, anterior and compartments. Inside the capsule there proliferated within a node can leave and posterior groups. is a supporting network of reticular fibres circulate to other parts of the body. It and fibroblasts. Within the capsule, the is lymphocyte proliferation that causes Level II – nodes lying deep to the parenchyma of the node is divided into lymphadenopathy [5]. pectoralis minor muscle including the specialist regions called the cortex and central nodes and possibly some apical the medulla [5]. Usually metastases are delayed by nodes. the reticular fibres and implant in the Level III – nodes lying medial and The cortex lies beneath the capsule and subcapsular and cortical sinuses of the superior to the pectoralis minor contains densely packed lymphocytes node. The metastatic cells proliferate and muscle – the apical group of axillary arranged in masses. Around the edge of eventually cause lymphadenopathy. In the lymph nodes [7,8]. the mass, which is called a follicle, are breast, foreign particles such as silicone lymphocytes called T cells, macrophages gel tend to be trapped and accumulate in and dendritic cells, which participate in the medulla [8]. Internal mammary nodes the activation of T cells. In the germinal The internal mammary nodes are small centre of the follicle are lymphocytes Changes in lymph nodes due to age nodes up to 6mm in diameter that called B cells, which proliferate into Normal lymph nodes undergo change accompany the internal mammary artery antibody-secreting plasma cells. over a person’s lifetime. Atrophy, cortical and vein. These nodes lie in the fat and thinning and scarring occur as a result connective tissue behind the intercostal The cortex surrounds the medulla, which of multiple episodes of infection and muscles and anterior to the pleura in is comprised of medullary cords of tightly inflammation. Scarring may lead to the first, second and third intercostal packed strands of lymphocytes, plasma asymmetric thinning of the cortex. As spaces within 20mm of the lateral cells and macrophages. atrophy occurs, the amount of fat within sternal border. The internal mammary the hilum increases. Fatty infiltration can nodes drain the medial portions of the Lymph enters the node through progress faster than atrophy, leading breast [8]. multiple afferent vessels, which pierce to an increase in the overall size of the the convex capsule. These vessels lymph node despite the atrophy of the Intramammary nodes contain valves that ensure the lymph cortex and medulla [8]. Lymph nodes are common findings in only flows in one direction – toward the breast. Intramammary nodes range the centre of the node. Once inside the Lymphadenopathy, atrophy, cortical in size from 3–10mm. They are usually node, the lymph flows through a series thinning, scarring, fatty infiltration found in the upper outer quadrant of the of irregular channels called sinuses. and metastatic involvement all cause breast including the axillary tail, but may Lymph flows through the cortical, then morphological changes in a lymph node be found in any quadrant [3,8]. the medullary sinuses and leaves the that can be detected on ultrasound [8]. node via the efferent vessels. The Structure and function of the efferent vessels leave the node at a lymph nodes slight depression called the hilum, Ultrasound appearance of Lymphatic vessels drain tissues of where the artery and vein also enter normal lymph nodes excess interstitial fluid, returning it to the and exit. There are only one or two blood. This fluid can also contain waste efferent vessels, which are larger than On ultrasound, normal lymph nodes are products, microbes and other particles. the afferent vessels [5]. well defined, reniform or coffee bean ISSUE 3 2009 O 17 ask the expert Lymph nodes in breast ultrasound shaped masses with a hypoechoic cortex. Fatty infiltration can also cause a Shape cortex and a hyperechoic central portion node to become more rounded [8]. As described earlier, normal lymph representing the medulla. In the short nodes are reniform or coffee bean axis, the hypoechoic cortex of the node shaped (fig 2). Enlargement due to is C-shaped surrounding the hyperechoic Ultrasound appearance of inflammation and infection tend to medulla (fig 2). The medullary portion abnormal lymph nodes enlarge the lymph nodes in all planes of a lymph node is hyperechoic due maintaining their typical shape. to the multiple interfaces between the Due to age changes, overall size and Metastases can enlarge the node medullary cords and sinuses that are shape of nodes can have limitations for so that they become more rounded. perpendicular to the ultrasound beam [8]. predicting abnormalities. Assessment However, as already stated, fatty The blood vessels enter and leave at the of the morphological features of the infiltration can also cause rounding (fig hilum of the node. Power Doppler can be capsule, cortex and medulla are 3), as can severe cases of necrotising used to demonstrate the artery entering more important for the detection of lymphadenitis [8]. the echogenic medulla, even in small abnormalities [1,3,4,8]. It is also important nodes [3,8]. to note that there is overlap of features Echogenicity for both benign and malignant diseases. The cortex of abnormal nodes usually As the patient ages the hypoechoic becomes more hypoechoic. This is cortex can become thinner due to Size because of the proliferation of cells. atrophy. Scarring due to repeated The normal size range of lymph nodes is This proliferation can be due to either episodes of infection and inflammation reported to be from 1mm to 25mm [5]. benign or malignant causes [1,8]. One can also cause the hypoechoic cortex As described above, fatty infiltration can should be guarded if harmonics is used to become lobulated or almost absent cause an increase in the overall size of to better identify nodes in fatty tissue, as in parts. The cortex may become more the lymph node despite the atrophy of the cortex will appear more hypoechoic – isoechoic with the surrounding fat, the cortex and medulla (fig 3). As a result, this should not be mistaken for an making the node difficult to visualise. nodes seen on imaging can measure up abnormality [8]. Harmonics can be used to make the to 50mm in length [1]. This makes size a cortex more conspicuous, allowing the poor predictor of abnormality [1,2,3,8]. Eccentric cortical thickening node to be identified and assessed [8]. Uniform cortical thickening is usually the Stavros (2004) suggests that the short- result of inflammation, infection Fatty infiltration due to atrophy begins at axis measurement of a node greater or a systemic process [3]. As metastases the hilar notch, enlarging the echogenic than 10mm is a more useful sign of an are more likely to implant in the cortex, hilum. As demonstrated in figure 3, the abnormality. However, Stavros himself they can cause focal thickening and hilum becomes more hypoechoic as the warns that many fatty infiltrated nodes decreased echogenicity of the cortex. fatty infiltration increases. The remaining can be greater than 10mm in the short- Figure 4 demonstrates this abnormal hyperechoic portions of the medulla axis diameter, and some metastatic appearance. In scarred nodes, become compressed and can be visible nodes that are morphologically abnormal inflammation can also cause focal as a thin echogenic rim adjacent to the will be less than 10mm [8]. bulges [1,3,4,8]. cortex , cortex medulla medulla 14L7 14L7 Fig 3. Normal node with cortical thinning T14.0 T140 and fatty infiltration. The medulla is compressed into a thin echogenic line Fig 2. Normal lymph node imaged in the long and short axis. surrounding the hypoechoic fatty hilum. O 18 soundeffects Lymph nodes in breast ultrasound ask the expert Eccentric medullary compression In the same way an expanding metastasis can cause cortical bulges, it can also cause eccentric compression of the echogenic medulla, which is also demonstrated in figure 4. Contrast this with figure 5, which demonstrates uniform compression of the medulla, secondary to inflammation. Eventually metastases may involve the entire cortex and also cause more uniform 14L7 14L7 . T14.0 T14.0 compression of the medulla [8]. Fig 4. Abnormal lymph node with a focal bulge in the cortex and eccentric compression of Convex inward focal compression of the medulla. the medulla 8HZ 8H Similar to eccentric compression, metastases can cause focal cortical bulges into the medulla without causing capsular bulges. Stavros (2004) uses the term ‘rat bites’ to describe this appearance [8]. These convex bulges into the medulla can also be observed with inflammation but they tend to be multiple, Fig 5. Benign reactive node with uniform compression of the medulla seen as a thin uniform and smaller [8]. echogenic line. Medullary displacement Severe eccentric cortical thickening that displaces the medulla to one edge of the node rarely occurs with inflammation and is more specific for metastases, such as the abnormal node seen in figure 6 [8]. Medullary obliteration The medulla and hilar fat can be completely obliterated by metastases, such as has occurred with the lymph 1417 node seen in figure 7. This can occur in Fig 6. Long- and short-axis images of an abnormal node with severe eccentric cortical cases of severe inflammation but is more thickening that displaces the medulla to one edge of the node. common in metastatic disease [1,3,4,8]. Loss of thin echogenic margins In the presence of perinodal invasion the capsule is breached, resulting in irregular angular margins or spiculations, also demonstrated in figure 7 [1,3,8]. Doppler and blood flow Doppler can be used to further assess abnormal nodes. There is usually only one artery and vein leaving the node via the Fig 7. Multiple metastatic lymph nodes where the medulla and hilum have been obliterated. hilar notch. Power Doppler can readily be Perinodal invasion has occurred in one node resulting in irregular ill-defined margins. used to identify the artery. Inflammation ISSUE 3 2009 O 19 ask the expert Lymph nodes in breast ultrasound 1215 1215 + 3 12.0 12.0. CF 5,3 16 fps 8 fps Fig 8. Marked vasodilation and increased Fig 9. Abnormal lymph node with hypoechoic cortical thickening, eccentric medullary blood flow demonstrated using power compression, perinodal invasion and blood flow crossing the convex capsule of the node. Doppler in a patient with lymphoma. can extend into the axilla. If the patient It is important to optimise the focal can cause vasodilation and increased presents with palpable nodes or if a zones, depth and gain to ensure the deep blood flow into the node via the feeding breast cancer has been identified, the axillary vessels are visualised. The use of artery as in figure 8 [4]. However, as axilla is always carefully assessed for harmonics often improves the contrast with cancers in other parts of the body, evidence of metastatic spread to the between the cortex and axillary fat. neo-vascularisation can occur. This can axillary lymph nodes. result in multiple feeding vessels or the Transverse scans of the axilla are formation of vessels that cross the capsule The patient should be placed in the performed by rotating the transducer of the node which are seen with Doppler supine oblique position with their arm 90o and moving inferiorly from the head flow [8]. Figure 9 shows an example of raised above their head so that the of the humerus down the axilla in slow neo-vascularisation in an abnormal node. surface of the axilla is as flat as possible. overlapping sweeps until the entire axilla It is difficult to scan a concave axilla. The has been scanned. axilla is then assessed using transverse, Scanning technique and sagittal and oblique scans. Rotter’s nodes and level II and level image documentation III nodes can be visualised if they Initially the transducer, orientated are abnormal by moving medially The lower axillary nodes (pectoral) sagittally, is placed 20 or 30mm medial and superiorly from the edge of the and intramammary nodes are routinely to the edge of the pectoralis major pectoralis major muscle. The pectoralis seen on transverse, sagittal and radial muscle at the level of the axillary tail. minor muscle can be seen directly below survey scans of the breast. The pectoral The transducer is moved laterally over pectoralis major. Rotter’s nodes are nodes are usually seen in the transverse the edge of the pectoralis major muscle. located between these muscles (fig 1). scans that overlap the lateral edge of Lymph nodes can usually be seen in the Level II nodes can be traced medially the breast. If these nodes demonstrate axillary fat just adjacent to the edge of between the pectoralis minor muscle normal morphology, they are considered the pectoralis muscles. The transducer and the axillary vein. Medial to the normal anatomy and are not routinely is then slowly swept from pectoralis pectoralis minor muscle is the level III documented. If these nodes appear major to latissimus dorsi muscle in a region [3]. abnormal or correspond to a clinical series of overlapping scans gradually lump or mammographic density under moving superiorly. In addition, it can be If any of the axillary nodes appear investigation, they are imaged in four useful to angle the probe from side to abnormal, they are imaged in sufficient planes (transverse, sagittal and both side varying the compression during the planes to demonstrate morphology, obliques), measured and blood flow sweeps of the transducer if it is proving measured, and blood flow demonstrated demonstrated with power Doppler. difficult to identify nodes. In thin patients with power Doppler. In the absence the lymph nodes are usually easily of abnormal nodes, one or two The axilla identified superficially. In larger patients representative images of the axilla The axilla should be routinely investigated significant compression may be required are documented. Nodes with normal and imaged as accessory breast tissue due to the thickness of the axillary fat. morphology are not measured. O 20 soundeffects Lymph nodes in breast ultrasound ask the expert Internal mammary nodes It is rare that abnormal nodes are the metastases in breast cancer: A systematic If a patient has a medial breast cancer, the first manifestation of a breast cancer. review. AJR. 2006 May;186(5):1342–8. parasternal region should be scanned in If no cause for an abnormal lymph node 3. Madjar H, Mendelson EB. The an attempt to identify metastatic lymph is identified in the breast, it is important practice of breast ultrasound. 2nd ed. nodes. These nodes may be difficult to to ask the patient about their medical Stuttgart:Thieme; 2008. see unless they are enlarged [3,9]. Once history. Consideration should be given 4. Dixon A. Malignant breast disease, Chapter again, the use of harmonics may help to inflammation or infection, recent 7 of Breast ultrasound: How, why and to distinguish them from surrounding surgery or biopsy involving the upper when. 1st ed. Dixon A, editor. Edinburgh: structures. The use of colour Doppler to limb and the upper body, Churchill Livingstone Elsevier; 2007. delineate the blood vessels may also help lymphoproliferative diseases, or other 5. Tortora GJ, Grabowski SR. Principles of to identify these nodes. Due to their size known malignant or autoimmune anatomy and physiology. 8th ed. New York: and surrounding structures it is not usually diseases [1]. It may also be prudent Harper Collins; 1996. possible to assess the morphology [8]. to reassess the breast tissue and any 6. Cardenosa G. Breast imaging companion. seemingly benign lesions, looking for 2nd ed. Philadelphia: Lippincott Williams & any evidence of a subtle breast Wilkins; 2001. Summary cancer that may have otherwise been 7. Stocksley M, Dixon A. Breast anatomy and overlooked. normal ultrasound appearance, Chapter 3 With the correct scanning technique, of Breast Ultrasound: How, why and when. lymph nodes are readily identified in 1st ed. Dixon A, editor. Edinburgh: Churchill References Livingstone Elsiever; 2007. the breast and axilla. As is the case with breast tissue, there is variation in the 8. Stavros AT. Breast ultrasound. 1st ed. normal ultrasound appearance of nodes 1. Heywang-Kobrunner SH, Dershaw DD, Philadelphia: Lippincott Williams & Wilkins; 2004. with age and overlap of the features of Schreer I. Diagnostic breast imaging. 2nd benign and malignant disease. Careful ed. Stuttgart:Thieme; 2001. 9. Dixon A. Ultrasound examination assessment of morphology is required. technique, Chapter 4 in Breast ultrasound: 2. Alvarez S, Anorbe E, Alcorta P, Lopez F, How, why and when. 1st ed. Dixon A, Biopsy is usually necessary for Alonso I, Cortes J. Role of sonography editor. Edinburgh: Churchill Livingstone a definitive diagnosis. in the diagnosis of axillary lymph node Elsevier; 2007. Australian Medical Couches 69 Hardiman Street Telephone:03 9376 0060 Kensington Vic 3031 Facsimile: 03 9376 0606 Web: www.australianmedicalcouches.com · GENERAL ULTRASOUND · VASCULAR ULTRASOUND · O&G ULTRASOUND · . ECHO ULTRASOUND . & CUSTOM BUILT TABLES . ISSUE 3 2009 C 21