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Lymphadenitis & Lymphadenopathy

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Authors

M. Terese Whipple, MD
Department of Emergency Medicine
University of Iowa Hospitals and Clinics

Christopher Hogrefe, MD, FACEP, CAQ-SM
Department of Emergency Medicine
University of Iowa Hospitals and Clinics
Assistant Team Physician, Chicago Cubs

Summary

  • Benign or reactive lymph nodes are typically oval, hypoechoic, have an echogenic hilum, hilar vascular flow, and blurred borders. 
  • Malignant nodes are more often round with a loss of the echogenic hilum and peripheral or mixed vascular flow. 
  • Malignant nodes can have central necrosis similar in appearance to suppurative nodes; however, suppurative nodes will often have surrounding inflammation and a history more consistent with infection rather than malignancy. 
The lymphatic system (click to enlarge)
  • All characteristics seen on ultrasound must be considered together, as there can be considerable overlap in appearance between pathologies.
US normal cervical lymph node chain
Normal cervical lymph node chain[1]Ying M, Lee YYP, Wong KT, Leung VYF, Ahuja AT. Ultrasonography of Neck Lymph Nodes in Children. Honk Kong Journal of Pediatrics. 2009;14:29-36
US normal cervical lymph node
Normal cervical lymph node. Fatty echogenic hilum (arrow) in the center is preserved, and shape index is <0.5[2]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
Reactive lymph node which demonstrates an abnormally enlarged 3.o cm hypoechoic node corresponding to a painful, palpable lump.[3]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
Metastatic lymph node in a patient with known renal cell carcinoma demonstrates an enlarged, round, hypoechoic, heterogeneous lymph node (arrow) with lack of fatty hilum [4]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.

Introduction

  • Lymphadenopathy is a common chief complaint in the Emergency Department (ED), especially among pediatric patients.
  • There are many benign causes of lymphadenopathy, the most common of which is reactive lymph nodes from nearby infection or inflammation.[5]Leung AKC, Davies HD. Cervical lymphadenitis: etiology, diagnosis, and management. Curr Infect Dis Rep. 2009;11(3):183-189. Additionally, up to 90% of healthy children ages 4 to 8 years old may have palpable lymph nodes.[6]Ludwig BJ, Wang J, Nadgir RN, Saito N, Castro-Aragon I, Sakai O. Imaging of cervical lymphadenopathy in children and young adults. AJR Am J Roentgenol. 2012;199(5):1105-1113. However, there are several more concerning etiologies that should not be missed such as tuberculosis, lymphoma, and metastatic cancer.
  • Despite over 600 lymph nodes in the body, only those in the submandibular, axillary, and inguinal regions are palpable in healthy individuals, thus the determination of the size and cause of enlarged lymph nodes is not possible by physical examination alone.
  • Ultrasound has proven a valuable tool in the evaluation of enlarged lymph nodes both in the ED and outpatient clinics.[7]James V, Samuel J, Ong GY-K. Point-of-care ultrasound for evaluating lymphadenopathy in the pediatric emergency department: Case series and review of literature. J Emerg Med. 2020;59(1):75-83.However, no single sonographic criteria can accurately differentiate between benign and malignant causes of lymphadenopathy.[8]Loh Z, Hawkes EA, Chionh F, Azad A, Chong G. Use of ultrasonography facilitates noninvasive evaluation of lymphadenopathy in a lymph node diagnostic clinic. Clin Lymphoma Myeloma Leuk. … Continue reading Instead, a composite of several different characteristics combined with a thorough history and physical examination can provide an accurate diagnosis and appropriate disposition for patients in the ED.
  • Understanding of the different ultrasound characteristics of benign and malignant lymph nodes can aid in the prompt disposition of patients in the ED and ensure optimal follow-up.
  • Differentiating a lymph node from an abscess or hematoma is also important when considering procedures in areas where lymph nodes are present (e.g., axilla, inguinal region).

Lymphadenopathy Differential Diagnosis

  • Infection
    • Bacterial
      • Cutaneous/local infection (staphylococcus or streptococcus)
      • Bartonella (cat scratch disease)
      • Haemophilus ducreyi (chancroid)
      • Syphilis
      • Lymphogranuloma venereum
      • Tuberculosis
      • Tularemia
    • Viral
      • Adenovirus
      • Cytomegalovirus (CMV)
      • Epstein-Barr virus (EBV or mononucleosis)
      • Hepatitis
      • Herpes zoster
      • Human Immunodeficiency Virus (HIV)
    • Granulomatous
      • Histoplasmosis
      • Cryptococcus
      • Coccidioidomycosis
      • Berylliosis
      • Silicosis
    • Fungal
    • Lyme disease
    • Rickettsial diseases (e.g., Rocky Mountain Spotted Fever, Erlichiosis)
  • Malignancy
    • Lymphoma
    • Leukemia
    • Metastatic cancer
    • Kaposi sarcoma
  • Autoimmune
    • Sarcoidosis
    • Rheumatoid arthritis
    • Systemic lupus erythematosus
    • Sjögren’s syndrome
    • Dermatomyositis
  • Medication-induced
    • Phenytoin
    • Penicillin
    • Cephalosporins
    • Allopurinol
    • Atenolol
    • Carbamazepine
    • Sulfonamides
  • Serum sickness
  • Kawasaki disease

Lymph Node Anatomy

  • Each lymph node is encased in a dense connective tissue capsule.
  • The peripheral portion of the node is known as the cortex and is comprised of the lymphoid follicles.
  • The inner portion of the node is known as the medulla and is made up of cords and sinuses where lymph flows from afferent lymphatic vessels. 
  • The central hilum contains the lymphatic artery and vein, as well as the efferent lymphatic vessel.
lymph node illustration
Anatomy of a lymph node

Transducer Choice & Ultrasound Protocol

  • A high-frequency transducer (at minimum 7.5 MHz) should be utilized for ultrasound examination of cervical lymph nodes.[9]Ying M, Ahuja AT. Ultrasound of neck lymph nodes: How to do it and how do they look? Radiography. 2006;12(2) Linear transducers are usually most advantageous, although depending on body habitus a curvilinear may occasionally be necessary to assess deeper nodes in the axillary or inguinal region depending on a patient’s body habitus.
  • Each area should be evaluated for lymph node size, shape, borders, echogenicity, hilar appearance, and blood flow. The surrounding soft tissues should be assessed for any signs of inflammation as well.
  • Each lymph node should be evaluated in short (transverse) and long (longitudinal) axes to properly assess size.
  • Cervical Evaluation
    • For a cervical node evaluation, the patient should assume a supine position on the bed with the shoulders supported by a pillow. Head position should change throughout the exam to facilitate access to different lymph nodes as needed.
    • Hajek et al. established a classification system that separates cervical nodes into eight regions that can be used to clearly report the location of the findings. [10]Hajek P, Salomanowitz E, Turk R, Tscholakoff D, Kumpan W, and H Czembirek. Lymph nodes of the neck: evaluation with US. Radiology. 1986. 158:739-42.
AJCC classification of pathologic cervical lymph nodes
Diagram demonstrating the division of the neck into eight regions to classify lymph node location with ultrasound.[11]Chan JM, Shin LK, Jeffrey RB. Ultrasonography of abnormal neck lymph nodes. Ultrasound Q. 2007;23(1):47-54.
    • Remember that enlarged nodes in the supraclavicular region should be considered pathologic until proven otherwise
  • Axillary Evaluation
    • When evaluating the axillary region, the patient should be supine or propped into a supine-oblique position with the arm held abducted and externally rotated over the head.
    • A high-frequency transducer is typically the best choice for evaluation of this region; however, a curvilinear transducer may be necessary depending on body habitus and location of the lymph node in question in relation to fat pads in the area.[12]
  • Inguinal Evaluation
    • The patient should be placed in a supine position with the leg externally rotated at the hip and the knee flexed (i.e., “figure 4” position). If this is uncomfortable for patients, they may simply lie supine.
    • Superficial inguinal lymph nodes are superficial to the femoral vessels.[12]Jacobsen J, Khory V and C Brandon. Ultrasound of the groin: techniques, pathology, and pitfalls. AJR. 2015. 205:513-523.
    • Deep inguinal lymph nodes are located deeper and more medial to the femoral vessels.
    • Again, a high-frequency transducer is best for evaluating structures in detail, but body habitus may necessitate the use of a lower frequency curvilinear transducer.

Ultrasound Characteristics

Shape

  • Normal lymph nodes are typically oval or kidney shaped. [13]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
  • Reactive lymph nodes generally maintain an oval shape as the lymph node is uniformly affected by infectious/inflammatory pathogens and lymphoproliferation occurs diffusely.
  • Malignant nodes often become more round in shape.[14]Gupta A, Rahman K, Shahid M, et al. Sonographic assessment of cervical lymphadenopathy: role of high-resolution and color Doppler imaging. Head Neck. 2011;33(3):297-302.
Ultrasound of a normal lymph node
Ultrasound of a reactive lymph node
Ultrasound of a malignant lymph node
Video of a normal lymph node with blood flow (center area). Note the arterial and venous flow to the right of the video.
  • To better quantify lymph node shape, a short axis-to-long axis ratio (S/L) can be calculated. Benign nodes with an oval shape usually have a long axis at least twice their short axis, yielding an S/L ratio of less than 0.5. [15]Vassallo P, Edel G, Roos N, Naguib A, Peters PE. In-vitro high-resolution ultrasonography of benign and malignant lymph nodes: A sonographic-pathologic correlation. Invest Radiol. 1993;28(8):698-705.] Malignant nodes, which are more round in shape, tend to have an S/L ratio of greater than 0.5. It is normal for submandibular and parotid nodes to be more round with an S/L ratio greater than 0.5.
  • Evaluation of the shape of lymph nodes has proven reliable in differentiating between benign and malignant nodes. However, it should be noted that normal submandibular and parotid nodes can be round in shape. Thus, this criteria cannot be applied consistently to these locations. [16]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515. Additionally, infectious mononucleosis and cytomegalovirus (CMV) can cause round nodal enlargement as well. [17]Fu XS, Guo LM, Lv K, et al. Sonographic appearance of cervical lymphadenopathy due to infectious mononucleosis in children and young adults. Clin Radiol. 2014;69(3):239-245.[18]Restrepo R, Oneto J, Lopez K, Kukreja K. Head and neck lymph nodes in children: the spectrum from normal to abnormal. Pediatr Radiol. 2009;39(8):836-846.
Ultrasound lymph node measurement in long axis
Ultrasound lymph node measurement in short axis

Size

  • Size has traditionally been used to differentiate malignant from benign nodes: however, recent literature has shown size to be rather unreliable in differentiating pathologies.  [19]Chan JM, Shin LK, Jeffrey RB. Ultrasonography of abnormal neck lymph nodes. Ultrasound Q. 2007;23(1):47-54.
  • Reactive nodes, while often smaller than malignant nodes, can also experience significant enlargement due to hyperplasia, making size an unreliable criterion. 
  • Additionally, submandibular nodes tend to be larger than nodes found in the remainder of the neck, measuring up to 6 mm.[20]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
  • A recent study by Loh et al proposed a 2 cm cutoff, with nodes <2 cm more likely to be reactive; however, no consensus exists on this subject. [21]Loh Z, Hawkes EA, Chionh F, Azad A, Chong G. Use of ultrasonography facilitates noninvasive evaluation of lymphadenopathy in a lymph node diagnostic clinic. Clin Lymphoma Myeloma Leuk. … Continue reading

Borders

  • Generally, reactive lymph nodes are considered to have blurred borders, likely due to surrounding tissue inflammation. [22]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
  • Malignant nodes tend to have sharp borders likely due to tumor infiltration as well as loss of intranodal fat. This increases the acoustic impedance. [23]Chan JM, Shin LK, Jeffrey RB. Ultrasonography of abnormal neck lymph nodes. Ultrasound Q. 2007;23(1):47-54.[24]Gupta A, Rahman K, Shahid M, et al. Sonographic assessment of cervical lymphadenopathy: role of high-resolution and color Doppler imaging. Head Neck. 2011;33(3):297-302.
  • Malignant nodes can also have irregular borders with areas of focal widening due to focal tumor invasion causing blockage of lymphatic channels. [25]Prativadi R, Dahiya N, Kamaya A, Bhatt S. Chapter 5 ultrasound characteristics of benign vs malignant cervical lymph nodes. Semin Ultrasound CT MR. 2017;38(5):506-515.
Ultrasound lymph node blurred borders, tissue inflammation
Ultrasound lymph node malignant, irregular border
Ultrasound lymph node malignant with acoustic impedence
  • Unfortunately, blurred borders cannot definitively exclude malignancy, as malignant nodes with extra-capsular spread of the tumor can have a similar appearance.  [26]Chan JM, Shin LK, Jeffrey RB. Ultrasonography of abnormal neck lymph nodes. Ultrasound Q. 2007;23(1):47-54.
  • Matting, or the blending of borders of adjacent lymph nodes together with no intervening soft tissue between, can also be seen in malignant and tuberculous lymph nodes.[27]Park JH, Kim DW. Sonographic diagnosis of tuberculous lymphadenitis in the neck. J Ultrasound Med. 2014;33(9):1619-1626. Infectious mononucleosis can also cause matting, which often occurs bilaterally.[28]Fu XS, Guo LM, Lv K, et al. Sonographic appearance of cervical lymphadenopathy due to infectious mononucleosis in children and young adults. Clin Radiol. 2014;69(3):239-245. Conversely, matting in tuberculous (TB) lymph nodes is almost always unilateral.

Nodal Echogenecity

  • Normal lymph nodes appear hypoechoic compared to surrounding tissue and have an echogenic hilum composed of lymphoid sinuses, vasculature, and fatty tissue. 
  • Reactive lymph nodes are enlarged due to hyperplasia of normal lymph tissue and therefore typically maintain this architecture. 
  • Malignant nodes can have a relatively hypoechoic cortex as well, and should be evaluated for the other features described in this chapter (e.g.  size, shape, presence of echogenic hilum and blood flow patterns to help distinguish malignant from benign pathology.) 
Ultrasound normal lymph node with echogenic hylum
  • Papillary thyroid cancer can cause nodes to appear hyperechoic relative to surrounding tissue, which is thought to be due to thyroglobulin production within the node. [29]Ahuja AT, Ying M. Sonographic evaluation of cervical lymph nodes. AJR Am J Roentgenol. 2005;184(5):1691-1699.
  • Kawasaki disease is traditionally described as a hypoechoic cluster of grapes on ultrasound. [30]Tashiro N, Matsubara T, Uchida M, Katayama K, Ichiyama T, Furukawa S. Ultrasonographic evaluation of cervical lymph nodes in Kawasaki disease. Pediatrics. 2002;109(5):E77-7.
  • Necrosis within a lymph node should usually be considered pathologic, as it is most often the result of a tumor outgrowing its blood supply. Cystic necrosis has the appearance of cystic anechoic areas within the node. Less commonly, coagulative necrosis can occur and cause hyperechoic areas that may be confused with the hilum. Rarely, inflammatory lymph nodes have areas of coagulative necrosis. However, these areas can be distinguished from the hilum as they are not continuous with perinodal fat.[31]James V, Samuel J, Ong GY-K. Point-of-care ultrasound for evaluating lymphadenopathy in the pediatric emergency department: Case series and review of literature. J Emerg Med. 2020;59(1):75-83.
Ultrasound normal lymph node with necrosis
Ultrasound lymph node with micronodular reticular appearance
  • Calcifications within a node indicate malignancy, most often papillary thyroid carcinoma metastasis. Medullary thyroid carcinoma can also cause calcification, as well as prior chemotherapy, radiation, and rarely TB. They are not seen with reactive nodes.
  • Nodes that appear so hypoechoic that they have a cystic appearance are concerning for lymphoma. These nodes are often enlarged and round in shape, and with lower resolution transducers can cause posterior acoustic shadowing. Higher resolution transducers may reveal thin septations within the node, giving it the typically described “micronodular reticular” appearance.[32]Ying M, Ahuja AT. Ultrasound of neck lymph nodes: How to do it and how do they look? Radiography. 2006;12(2)

Hilum

  • The hilum is echogenic and continuous with the connective tissue surrounding the lymph node. Lymph nodes with echogenic hila can generally be considered to be benign.
  • Hila are usually more obvious in larger nodes and in older patients who have more fatty infiltration of their lymph nodes.
  • Malignant nodes lose their hila due to tumor infiltration. In about 4% of cases, malignant nodes can maintain their echogenic hilum. [33]Ahuja A, Ying M. An overview of neck node sonography. Invest Radiol. 2002;37(6):333-342.
Ultrasound lymph node with normal hilum

Blood Flow

  • There are several different types of blood flow that can be observed in lymph nodes: [34]Ahuja A, Ying M. An overview of neck node sonography. Invest Radiol. 2002;37(6):333-342.
    • Hilar flow: signal branching radially from the hilum, which can originate from the cortical region and shows a regular course from the hilum
    • Capsular/peripheral flow: follows the periphery of the node that perforates from the periphery rather than originating from the hilum
    • Mixed hilar and peripheral flow: found in both the hilum and the periphery
    • Avascular: no signal
Description of lymph node with blood flow
  • Benign nodes will show hilar flow, and smaller nodes (< 5 mm) in short axis may be avascular.[35]Ahuja AT, Ying M. Sonographic evaluation of cervical lymph nodes. AJR Am J Roentgenol. 2005;184(5):1691-1699. Necrotic nodes can also be avascular. Therefore, evaluation of vascularity should always be combined with a greyscale evaluation of the previously mentioned features.
  • Malignant nodes will tend to have mixed or peripheral vascularity. Angiogenesis draws blood flow from the periphery, and tumor invasion can also displace blood toward the periphery. TB nodes can also show a similar pattern.[36]Na DG, Lim HK, Byun HS, Kim HD, Ko YH, Baek JH. Differential diagnosis of cervical lymphadenopathy: usefulness of color Doppler sonography. AJR Am J Roentgenol. 1997;168(5):1311-1316.

Blood Flow

  • The hypoechoic appearance of lymph nodes, especially those with a cystic appearance, may be difficult to differentiate from an abscess. 
  • The easiest way to distinguish an abscess from a lymph node is with color doppler. Abscesses should have no blood flow, and most lymph nodes will have peripheral or hilar flow. 
  • Also evaluate the grey scale image for the previously mentioned architecture typical of lymph nodes, including the hyperechoic hilum.

Splenic Ultrasound

  • No discussion of emergency ultrasound of the lymph system would be complete without the largest lymph organ: the spleen.
  • The spleen lies in the left upper quadrant of the abdomen situated between ribs 9 and 11.[37]Benter T, Klus L, and U Teichgraber. Sonography of the spleen. J Ultrasound Med. 2011. 30:1218-1293.
  • The diaphragm covers the superior, lateral, and posterior surfaces of the spleen. The left kidney lies inferomedially.[38]Andrews, MW. Ultrasound of the spleen. World J Surg. 2000. 24:183-187.
  • The average upper limit of normal splenic size is 11-12 cm in length; however, significant variability can occur depending on the patient’s height.
  • Ultrasound Technique
    • The spleen is best visualized using a posterolateral intercostal technique and a curvilinear (3.5 MHz – 7.5 MHz) transducer.[39]Andrews, MW. Ultrasound of the spleen. World J Surg. 2000. 24:183-187.
    • The transducer should be positioned longitudinally between ribs to minimize rib shadow and visualize the spleen in long axis.
    • The spleen moves superiorly and inferiorly with the diaphragm during respiration. It can be helpful to ask patients to breathe slowly and hold their breath once the spleen comes into view so the image can be optimized.
    • Once the spleen is visualized, the transducer should be angled anteriorly and posteriorly to examine the entire spleen. The transducer should be turned 90° to evaluate the spleen in short axis, although this image can be difficult to acquire due the narrow window between ribs, resulting in rib shadow.
  • Sonographic Appearance
    • The splenic parenchyma is homogenous with a uniform ecotecture that is more hyperechoic than adjacent renal tissue. It is surrounded by a thick, hyperechoic capsule.
    • Arterial and venous flow enters and exits the spleen through the hilum. When color doppler is applied, arterial blood flow can be seen branching from the hilum into the periphery.
Abdomen US Normal Spleen
Normal appearing spleen seen on the left.
  • Pathology
    • The most common indication for emergency ultrasound of the spleen is in the setting of a traumatic injury.
    • Blood is hypo- or anechoic if visualized acutely. However, as a hematoma organizes over one to two days it becomes more hyperechoic and may be difficult to distinguish from the splenic parenchyma. Blood will collect in the subcapsular space unless the capsule ruptures.
    • If the splenic capsule ruptures, blood will spill into the intraperitoneal space and become visible on a focused assessment with sonography in trauma (FAST) exam. Care should be taken to evaluate the entirety of the spleen to assess for surrounding blood.
    • Splenic lacerations can also be visualized on ultrasound and will show a fissure in the splenic parenchyma filled with blood.

Pearls and Pitfalls

  • Each ultrasound characteristic individually cannot be used to reach a diagnosis.  Instead, all of the characteristics should be considered together, in addition to the history and physical examination in order to increase the accuracy of the assessment and decrease the likelihood of the below pitfalls affecting the diagnosis.  Additionally, each patient should follow-up for re-evaluation to ensure that the lymphadenopathy resolves, or pursue further testing (e.g., FNA) if necessary. 
  • Vasculature in the neck can be confused with a hypoechoic, cystic appearing lymph node with no hilum. Doppler can be used to identify flow, and the structure should be traced cranial and caudal and evaluated in long axis to differentiate the two. 
  • Abscesses in the neck, axilla, or groin may be difficult to distinguish from lymph nodes on physical exam, and ultrasonography can be useful. However, like vasculature, a cystic appearing lymph node without a hilum may look like an abscess on ultrasound. In this case, doppler can again be helpful as abscesses should have no flow and lymph nodes will have hilar or peripheral flow.
  • Compression of the lymph node with heavy transducer pressure can impair the visualization of vasculature within the node. 
  • Suppurative lymph nodes can have areas that are irregular and hypoechoic, similar in appearance to the necrosis seen in malignant nodes. Suppurative nodes will often have surrounding soft tissue inflammation, whereas malignancy will not. In the case of an unclear diagnosis, FNA is necessary. [40]Białek EJ, Jakubowski W. Mistakes in ultrasound diagnosis of superficial lymph nodes. J Ultrason. 2017;17(68):59-65.
  • Lymphomatous nodes may mimic simple cysts, especially on lower resolution ultrasounds. 
  • Micro-metastasis (i.e., small or early infiltration of tumor, may have the same general appearance of a benign node. However, this is not exclusive to ultrasound, it may be missed on computed tomography (CT), magnetic resonance imaging (MRI), or with FNA biopsy.[41]Bialek EJ, Jakubowski W, Szczepanik AB, et al. Vascular patterns in superficial lymphomatous lymph nodes: A detailed sonographic analysis(). J Ultrasound. 2007;10(3):128-134.
PathologyShapeShapeHilumEchogenicityVascularity
LymphomatousRoundSharpAbsentHypoechoic; may appear cystic on low resolution ultrasound or show intranodal reticulationPeripheral or mixed
MetastaticRoundRoundAbsentHypoechoic; may have necrosisPeripheral or mixed
ReactiveOval
(Except submandibular and parotid, which may be round)		BlurredEchogenicHypoechoic compared to surrounding tissueHilar or avascular
SuppurativeOvalBlurred with surrounding inflammatory change. If an abscess has formed there may be a thickened, echogenOften absentPossible central necrosis and complexity with debris, septi, or foci of air
Increased hilar vascularity
TuberculousRoundBlended with surrounding nodes, or “matted”AbsentHypoechoic; may have cystic necrosisPeripheral or avascular

References

References[+]