What are the characteristic ultrasound features of lymphoma?

Characteristic Ultrasound Features of Lymphoma

Lymphoma typically appears as hypoechoic lesions on ultrasound with specific patterns that vary by location, most commonly showing homogeneous echogenicity, round or oval shape, and preserved internal architecture with characteristic vascular patterns. 1, 2

Nodal Lymphoma Features

B-Mode Characteristics

Lymph node morphology:

• Round or oval shape rather than the elongated shape of normal lymph nodes 1, 2
• Hypoechoic cortex with relatively homogeneous internal echo pattern 2, 3
• Sharp, well-defined margins that remain distinct even with enlargement 2, 4
• Preserved internal structure in early stages, though the normal echogenic hilum may be displaced or compressed 2
• Through transmission (posterior acoustic enhancement) is frequently present, distinguishing lymphoma from metastatic nodes 2

Pattern of involvement:

• Multiple discrete enlarged nodes are most common, appearing as multiple nodules (seen in approximately 66% of cases) 1
• Solitary mass pattern with irregular or lobular shape occurs in approximately 34% of cases 1
• Homogeneous inner echo with clear margins when presenting as multiple nodules 1

Color Doppler Features

Vascular architecture distinguishes lymphoma from other pathology:

• Abundant hilar flow is the hallmark finding, with preserved or slightly displaced central vasculature 2, 5
• Large arborized hilum may be displaced but remains visible on color Doppler 2
• Normal or slightly increased vascular resistance with resistance index (RI) typically <0.80, contrasting sharply with metastatic nodes (RI >0.80) 2
• Hilar vascularization pattern rather than the predominantly peripheral flow seen in metastases 2, 5

Specific Sonographic Signs

Diagnostic patterns helpful for lymphoma identification:

• "Cobblestone sign" - multiple adjacent enlarged nodes creating a cobblestone appearance 1
• Intranodular reticulation - internal linear echogenic structures 1
• "Vessels-embedded sign" - blood vessels coursing through the nodal mass 1
• Hilar vascularity maintained even with significant nodal enlargement 1

Organ Involvement Patterns

Gastrointestinal Lymphoma

When lymphoma involves the GI tract (particularly gastric):

• Hypoechoic lesion localized to the second and third layers (deep mucosa and submucosa) of the gastric wall 6
• May extend through the entire wall in more advanced cases 6
• Can be distinguished from other subepithelial masses by layer of origin and echogenicity 6

Abdominal Organ Infiltration

Solid organ involvement shows characteristic patterns:

• Liver and spleen are the most commonly involved abdominal organs after lymph nodes 3
• Four infiltration patterns are described: diffuse, small nodular, large nodular, and bulky type 4
• Organ enlargement with multiple variable-sized hypoechoic lesions are the most common findings 3
• Disturbance of normal echo texture by predominantly hypoechoic lesions 4

Anatomic Distribution

Location patterns in abdominal lymphoma:

• Retroperitoneal and mesenteric lymph nodes are most commonly involved (61% of abdominal cases) 1, 3
• Multiple nodal stations are typically affected simultaneously 3

Key Differentiating Features from Other Pathology

Distinguishing Lymphoma from Metastatic Nodes

Critical differences that favor lymphoma over metastases:

• Preserved hilar vascularization versus predominantly peripheral flow in metastases 2
• **RI typically <0.80** versus RI >0.80 in metastatic nodes 2
• Homogeneous hypoechoic appearance versus heterogeneous cortex with possible keratin deposits in metastases 2
• Sharp margins versus unsharp margins indicating extranodal spread in metastases 2
• Through transmission versus absent posterior enhancement in metastases 2

Distinguishing from Inflammatory Nodes

Features that separate lymphoma from reactive adenopathy:

• Round shape versus elongated shape in reactive nodes 2
• Normal to slightly increased RI versus RI <0.60 in acute lymphadenitis 2
• Preserved architecture versus possible abscess formation (anechoic areas) in severe inflammation 2

Clinical Pitfalls and Limitations

Important caveats when interpreting ultrasound findings:

• Tuberculous lymph nodes can mimic lymphoma on color Doppler due to vessel dislocation by granulomatous masses, appearing inhomogeneously hypoechoic and rounded 2
• Micrometastatic involvement may preserve hilar vascularization similar to lymphoma, making early-stage differentiation challenging 2
• Sensitivity of B-mode and Doppler features is limited with significant false-negative rates, requiring tissue confirmation 2
• Ultrasound findings must be combined with aspiration cytology or core biopsy whenever possible to improve diagnostic accuracy 2, 5

Recommended Diagnostic Approach

Optimal ultrasound evaluation strategy:

• Use high-frequency probes for both peripheral lymph nodes and solid organ assessment 5
• Apply color Doppler and B-flow techniques to evaluate nodal vasculature and vessel architecture 5
• Consider contrast-enhanced ultrasound (CEUS) for detecting and characterizing lymphatic organ infiltration 5
• Core biopsies should be preferred over fine needle aspiration for tissue diagnosis, with ultrasound guidance 5
• CEUS can prove residual viable tissue after chemotherapy or radiation therapy 5