Reference valuesReference values

Axillae — Reference values

Axillae — Reference values: Minimum axillary protocol, Typical normal axillary lymph node, Lymph-node cortex, Lymph-node shape, Lymph-node Doppler.

Interpret the axilla by context: palpable lump, suspicious breast finding, oncologic staging, postoperative setting, recent vaccination, skin infection or soft-tissue mass. ACR rates axillary ultrasound as usually appropriate for a palpable axillary lump and many breast-cancer scenarios; EUSOBI treats post-vaccine adenopathy as contextual when ipsilateral, recent and without suspicious breast imaging.

Measurements and reference values

MeasurementUsual valueNote
Minimum axillary protocolhigh-frequency linear transducer; side, palpable area, skin, subcutaneous tissue, accessory breast tissue, lymph nodes and vessels when relevantIn breast/oncology context, document the axillary level when possible: lateral to pectoralis minor, posterior to pectoralis minor or medial to pectoralis minor.complete: side, location, morphology and Doppler when indicatedacceptable focused exam: symptomatic area only, with limitation clearly describedincomplete: palpable lump or oncology context without nodal/correlated breast assessmentSource: ACR Appropriateness Criteria Imaging of the Axilla / AIUM-ACR breast ultrasound parameter
Typical normal axillary lymph nodeoval or gently lobulated, thin homogeneous cortex, preserved fatty hilumCortex thinner than 3 mm with a central echogenic hilum is the most used normal pattern; size alone is less reliable than morphology.consensus normal: cortex <3 mm, preserved hilum, oval shapeborderline: cortex 3-5 mm, diffuse and with preserved hilumconsensus abnormal: absent/replaced hilum, eccentric focal cortex or suspicious rounded shapeSource: Dialani et al. Insights Imaging 2015 / UCLA Radiology / Bedi AJR 2008
Lymph-node cortex<3 normal; 3-5 gray zone; >5 suspicious if there is no clear reactive explanation mmSome studies use 2.3-3 mm thresholds for sensitivity, but this increases false positives. The table therefore keeps isolated thickening with preserved hilum in yellow.normal: <3 mmgray zone: 3–5 mmsuspicious: >5 mm ou espessamento excêntricoSource: Bedi AJR 2008 / Deurloo-Br J Cancer / ECR axillary assessment
Lymph-node shapelong-axis/short-axis ratio ≥2 favors benignity; <2 suggests roundingAvoid abbreviations in learner-facing reports: write long axis and short axis. Round shape carries more weight when paired with hilum loss or eccentric cortex.oval: ratio ≥2indeterminate: ratio near 2 with preserved hilumrounded: ratio <2 with associated suspicious findingsSource: Axillary lymph node ultrasound reviews / Vassallo criteria
Lymph-node Dopplerhilar/central flow is more reassuring; peripheral, mixed or chaotic flow increases suspicionDoppler is adjunctive: absent flow does not exclude disease, and hyperemia can be reactive with vaccination, infection or hidradenitis.hilar or absent: compatible if morphology is benignreactive increase: central/hilar in an inflammatory contextperipheral/disorganized: especially with lost hilum or suspicious breast massSource: Axillary node ultrasound morphology reviews
Accessory axillary breast tissueechotexture similar to breast, may contain cysts, fibroadenoma or malignancy like ordinary breast tissueIf there is a true focal lesion in accessory breast tissue, describe it with the breast lexicon and BI-RADS category according to local context.typical accessory tissue: no focal massprobably benign finding: simple cyst or typical fibroadenomasuspicious lesion: irregular mass, not parallel, suspicious calcifications or skin retractionSource: ACR BI-RADS / axillary mass reviews
Hidradenitis, abscess and axillary skindermal thickening, tracts/tunnels, collections, debris and peripheral hyperemiaUltrasound helps separate lymph node, drainable abscess, skin fistula, epidermal cyst and cellulitis. Gas, deep collection or systemic signs increase urgency.normal skin: no collection or tractinflammatory: thickening, hyperemia or superficial tractcomplicated: drainable abscess, gas, deep collection or immunosuppressionSource: Hidradenitis suppurativa ultrasound reviews / DERMUS

Classifications and calculators

Quick assistant — axillary lymph node

OutputColorInterpretation
Typical normalGreenOval, preserved fatty hilum, cortex <3 mm and hilar/absent flow.
Reactive/indeterminateYellowCortex 3-5 mm, diffuse thickening with preserved hilum, recent vaccination/infection or incomplete context.
SuspiciousRedAbsent/replaced hilum, eccentric focal cortex, round shape, peripheral/chaotic flow or associated breast/oncology finding.

The output is a teaching triage, not a replacement for BI-RADS, local oncology protocol or biopsy decision.

Source: ACR Imaging of the Axilla / Bedi AJR 2008 / EUSOBI 2023

Bedi-like morphologic classification — teaching version

TypeColorMorphologyPractical reading
1GreenNo visible cortex or extremely thin cortexTypical benign if context agrees.
2GreenThin cortex up to 3 mm, preserved hilumConsensus normal.
3YellowDiffuse cortical thickening, usually >3 mm, preserved hilumMay be reactive; compare side, vaccination, skin and breast.
4YellowLobulated or focal cortical thickening with hilum still identifiableMore concerning than type 3; depends on context and biopsy access.
5RedProminent focal cortex or marked partial hilum replacementSuspicious, especially in breast cancer or melanoma.
6RedAbsent/replaced hilum, rounded node or nodal massConsensus morphologic abnormality.

Publications vary: some group types 1-4 as benign and 5-6 as suspicious; in this reference type 4 is yellow because it is a decision zone.

Source: Bedi et al. AJR 2008 / axillary node reviews

Clinical context — when to raise the color

ScenarioSuggested colorHow to use in the report
No breast finding, no prior cancer, typical nodesGreenDescribe as usual-appearing lymph nodes if the symptom area was covered.
Recent vaccine or ipsilateral skin infection, no suspicious breast findingYellowReport as probably reactive when morphology is not frankly suspicious; follow local policy.
Postoperative setting, lymphedema or radiotherapyYellowCompare with prior studies and document scar/seroma/sentinel-node change if applicable.
Suspicious breast finding or known breast cancerRedDescribe side, axillary level, cortex, hilum, shape, Doppler and consider sampling according to protocol.
Melanoma, lymphoma, known metastasis or non-nodal solid massRedDo not close as reactive without correlation; may need biopsy, MRI or CT according to the hypothesis.

Source: ACR Appropriateness Criteria / EUSOBI vaccination guidance / oncologic axilla reviews

Differential diagnosis of an axillary mass

Ultrasound patternPossibilitiesWarning
Tissue with breast-like echotexture, no focal massAccessory breast tissueGreen only if there is no focal lesion.
Superficial collection with debris or peripheral hyperemiaAbscess, hidradenitis, inflamed epidermal cystRed if gas, deep collection, fever or immunosuppression.
Compressible superficial fatty lesionLipoma, accessory fat, rare herniaYellow if deep, painful, growing or not fully seen.
Non-fatty solid mass or infiltrative marginMetastasis, lymphoma, nerve-sheath tumor, sarcoma, advanced skin lesionRequires correlation and planned imaging/sampling.
Vascular, pulsatile or compressible lesion with flowVarix, vascular malformation, pseudoaneurysm, fistulaColor and spectral Doppler before puncture.

Source: ACR Imaging of the Axilla / soft-tissue ultrasound reviews

Report checklist — axillae

ItemWrite clearly
Side and locationRight/left axilla; palpable area; axillary level when relevant; relationship to scar or skin.
Lymph nodeLong axis, short axis, cortical thickness, fatty hilum, shape, margins and Doppler.
Breast contextWhether there is suspicious breast lesion, prior surgery, radiotherapy, lymphedema, recent vaccine or skin infection.
Non-nodal massAnatomic layer, content, vascularity, relationship to skin/fascia/vessels and whether it was fully seen.
ConclusionUse abbreviation-free wording: typical normal, probably reactive, indeterminate or suspicious; state the local next step.

Source: ACR / BI-RADS reporting principles / EUSOBI

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