Neck vs. Axillary Lymph Nodes: What Sonographers Should Know

Knowing the difference between documenting lymph nodes in the neck verses the axilla, though confusing, is important.

Axillary Lymph Nodes: What to Document

Axillary lymph nodes frequently respond to benign triggers such as infection, inflammation, or even recent vaccines.

What to Image

• Image all lymph nodes in the axilla with and without Color or Power Doppler.

• Display the hilum, shape, cortex, and vascularity clearly, showing the entire node ensuring you are not skewing it and making it appear lobular or abnormal.

When to Measure Cortex

• Measure the cortex when it is ≥ 3 mm.

• Measure the thickest cortex if multiple nodes exceed 3 mm.

Symmetry Matters

• If you find a 3 mm cortex or thicker on one side, always scan and document the contralateral axilla.

• Symmetry helps differentiate reactive nodes from something more suspicious.

When to Measure in Three Planes

Only measure lymph nodes in three planes if:

• The node has an abnormal appearance, such as:

  • Round shape/

  • Heterogeneous texture

  • Loss of fatty hilum

  • Increased vascularity

  • Irregular cortical thickening

Reactive normal appearing elongated nodes do not require three-plane measurement.

For more info and images on how to correctly image axilla lymph nodes, click here.

Neck Lymph Nodes: What to Document

Ultrasound assessment of the neck focuses on identifying lymph nodes within the major neck levels (I–VI) and distinguishing normal reactive findings from features suggestive of malignancy. Neck nodes can respond to infections, dental issues, thyroid conditions, or systemic inflammation.

What to Image

• Show all visualized lymph nodes with and without Power Doppler.

• Include images to demonstrate:

  • Shape

  • Hilum

  • Cortical thickness

  • Vascular pattern

Short Axis Evaluation, (note that cortex size is not a typical factor for the neck).

It is ideal to follow your companies protocol, but consider that short axis is a great guideline to follow. ACR mentions that short-axis enlargement and loss of the normal elongated morphology are suspicious findings. :

• Short axis, (the distance across the shortest axis, regardless of plane): The generally accepted normal short axis diameter is < 10 mm.

• 10-15mm can be normal in certain levels if it appears morphologically normal.

  • Normal: Oval, central fatty hilum, hypoechoic cortex and central hilum with normal vascularity.

When to Add Additional Views or Levels

• If a neck lymph node appears round, heterogeneous, or demonstrates abnormal vasculature, measure it in three planes.

Three-Plane Measuring

Measure in three planes only when the lymph node looks:

• Large

• Round

• Heterogeneous

• Vascular

• Lacking a fatty hilum