Lymph node evaluation comes up on nearly every neck, axillary, and groin scan. Knowing what makes a node normal, reactive, or suspicious changes what you document — and whether a patient gets a biopsy.

Normal Lymph Node Architecture

Understanding the normal appearance is everything in lymph node sonography.

Normal node sonographic features:

Oval shape — elongated, not round (short-to-long axis ratio, or S:L ratio < 0.5)
Hyperechoic fatty hilum — central echogenic fatty hilum with hilar vascularity on Doppler
Hypoechoic cortex — thin, uniform cortex surrounding the hilum
Hilar blood flow — Doppler flow enters through the hilum, branches peripherally (centripetal pattern)

Size: No universal cutoff, but general guidelines:

Cervical nodes: short axis (S) ≤ 10 mm considered normal; ≤ 8 mm in posterior triangle
Axillary nodes: S ≤ 10–15 mm; cortex ≤ 3 mm
Inguinal nodes: up to 15 mm S axis; inguinal nodes are normally somewhat larger
Jugulodigastric (level II): Up to 15 mm S axis is acceptable in the neck

Sonographic Criteria for Concern

No single feature reliably distinguishes reactive from malignant nodes — use the overall constellation of findings.

Shape: Roundness

As a node becomes infiltrated by tumor, it becomes more spherical.

S:L ratio (short-to-long axis ratio):

< 0.5: Normal, oval — favors reactive
0.5: More round — suspicious

A round node (S:L ≥ 0.5) in the neck or axilla deserves careful scrutiny even if small.

Hilum: Present or Absent?

The fatty hilum is the most important single feature.

Hilum	Interpretation
Present, normal	Strongly favors benign / reactive
Absent, replaced by cortex	Suspicious — loss of hilum suggests tumor infiltration
Hilar fat replaced by hypoechoic tissue	Suspicious

Exception: Submandibular and parotid area nodes may normally have less visible hila.

Cortex Thickness

Normal cortex is thin and uniform (≤ 3 mm). Eccentric or focal cortical thickening > 3 mm is suspicious.

Uniform (concentric) thickening → reactive (infection, inflammation)
Eccentric (focal) bulge → malignancy until proven otherwise

Vascularity Pattern

Normal: Hilar flow (enters at the hilum, fans out centrally).

Abnormal patterns:

Peripheral (capsular) vascularity — flow wraps around the node periphery or enters from the cortex → suspicious for malignancy
Absent vascularity — completely avascular node → may be necrotic (lymphoma, metastasis from squamous cell carcinoma)
Mixed pattern — both hilar and peripheral → indeterminate

Calcification

Punctate calcifications within a node strongly suggest papillary thyroid carcinoma metastasis (psammoma bodies). Also seen in treated lymphoma.

Coarse calcifications may represent prior granulomatous disease (TB, sarcoid) or treated malignancy.

Necrosis

Central necrosis appears as an anechoic or complex central area replacing the hilum. Associated with squamous cell carcinoma metastases and lymphoma.

Common Clinical Scenarios

Reactive Lymphadenopathy

The most common finding. Nodes are oval, have a preserved hyperechoic hilum, uniform cortical thickening, and hilar Doppler flow. Clinical context (recent infection, dental work, URI) confirms.

Typical example: Bilateral cervical adenopathy in a patient with pharyngitis. Nodes are enlarged but oval, have normal hila, and show symmetric hilar flow.

Metastatic Lymphadenopathy

Think about the primary tumor's drainage territory:

Neck nodes: Thyroid, nasopharynx, oropharynx, oral cavity, skin
Axillary nodes: Breast, upper extremity, skin
Inguinal nodes: Perineum, lower extremity, anorectal
Supraclavicular nodes (Virchow's): Lung, stomach, pancreas, lymphoma

Findings suggesting metastasis:

Round node (S:L > 0.5)
Absent or replaced hilum
Focal eccentric cortical bulge
Peripheral vascularity
Calcification (papillary thyroid)
Central necrosis

Lymphoma

Lymphoma nodes are often markedly enlarged, multiple, and may be matted (grouped). They tend to be round, have reduced or absent hila, and show disorganized internal vascularity. They are typically homogeneous and markedly hypoechoic ("pseudocystic" appearance).

Tuberculous Lymphadenopathy

Nodes may be matted, may show central necrosis, and occasionally calcify in chronic disease. Can be indistinguishable from metastatic nodes — biopsy is often needed.

Neck Levels: Know the Map

Radiologists and surgeons use a standardized cervical nodal level system. Knowing this helps you document node location properly.

Level	Location
I	Submental (Ia) and submandibular (Ib)
II	Upper jugular (above hyoid)
III	Middle jugular (hyoid to cricoid)
IV	Lower jugular (cricoid to clavicle)
V	Posterior triangle
VI	Central compartment (pretracheal, paratracheal)
VII	Superior mediastinum

Always document level when reporting cervical nodes. Example: "1.2 × 0.8 cm oval node at level IIA with preserved hyperechoic hilum."

When to Recommend Further Evaluation

Recommend additional imaging or biopsy when:

Short axis > 10 mm with loss of fatty hilum
Round node (S:L > 0.5) with eccentric cortical thickening
Peripheral (non-hilar) vascularity
Central necrosis or calcification
Matted or grouped nodes
Rapid growth on serial imaging
Clinical context: known malignancy, constitutional symptoms (B symptoms — fevers, night sweats, weight loss)

Reporting language for suspicious node: "1.4 cm short-axis lymph node at left level IIB with loss of the fatty hilum and eccentric cortical thickening. Peripheral vascularity on Doppler. Findings raise concern for metastatic or lymphomatous involvement. Correlation with clinical history and consideration of CT neck or biopsy are recommended."

Ultrasound-Guided Lymph Node Biopsy

When FNA or core biopsy is needed, ultrasound guidance improves yield by:

Targeting the most vascular, non-necrotic portion of the node
Avoiding major vessels
Confirming the needle tip position before sampling

You may be asked to assist or perform needle localization during biopsy. Document the procedure in your images.

SonoBuddy's small parts section includes thyroid, lymph node, and soft tissue evaluation guides.

Lymph Node Ultrasound: Normal vs. Pathologic Criteria