01OverviewDefinition, clinical context and the essential points that orientate the chapter.
An axillary lump may arise from a lymph node, skin, subcutaneous fat, an abscess or accessory breast tissue. Examination therefore begins by locating its anatomical compartment, then surveys both breasts, the upper limb and chest wall for a drainage-territory cause. Recent vaccination or infection may explain reactive nodes, while a hard persistent node, other nodal stations or constitutional symptoms widen concern to metastatic disease or lymphoma.
Ultrasound distinguishes nodal from non-nodal tissue and guides sampling, but the specimen plan must reflect the differential. Suspicious axillary adenopathy without a breast abnormality still requires breast imaging and nodal diagnosis. If lymphoma is plausible, early haematology and pathology coordination matters: excision is considered first under NG52, with core used when surgical risk outweighs benefit and feasible excision offered after a nondiagnostic core.
Key points
- Decide first whether the axillary lump is a lymph node, skin lesion, abscess, lipoma, vascular structure or hormonally responsive accessory breast tissue.
- Ask about breast symptoms, melanoma or other cancers, fever and weight loss, recent vaccination, upper-limb wounds, shaving, hidradenitis and pregnancy or lactation.
- Examine the lump’s depth, tenderness, mobility and skin relation, then assess both breasts, upper limbs, supraclavicular fossae and other nodal stations.
- NICE advises considering suspected-cancer pathway referral for an unexplained axillary lump in a person aged 30 or over.
- Axillary ultrasound characterises nodal morphology and guides sampling; normal breast palpation does not exclude an occult breast primary.
- If non-Hodgkin lymphoma is plausible, coordinate with haematology and pathology before sampling. NG52 considers excision first, core when excision risk outweighs benefit, and feasible excision after a nondiagnostic core.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Reactive and infective nodes
Recent vaccination, upper-limb or breast infection, skin trauma and systemic infection can stimulate axillary nodes; hidradenitis and abscess may instead arise within axillary skin structures.
Malignancy and non-nodal tissue
Breast carcinoma, lymphoma, melanoma or another malignancy can involve axillary nodes, while lipoma, epidermal cyst and accessory breast tissue form non-nodal masses.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Lymphatic immune response
Antigen drainage from the breast, thoracic wall and upper limb causes reactive follicular expansion, sometimes producing tender mobile nodes with preserved architecture.
- 2Metastatic replacement
Tumour cells entering afferent lymphatics can expand cortex, efface the fatty hilum and eventually fix or mat nodes to adjacent structures.
- 3Ectopic tissue change
Accessory axillary breast tissue responds to pregnancy and hormones and can develop the same benign or malignant lesions as pectoral breast tissue.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
A hard fixed node or matted nodal mass is concerning, whereas tenderness and mobility may accompany infection but are not reliable guarantees of benign disease.
Examine both breasts, chest wall, upper limb and nearby skin for malignancy, inflammation, vaccination reaction, wounds or hidradenitis that could explain reactive lymphadenopathy.
Epidermal cysts, lipoma, abscess, vascular lesions and hormonally responsive accessory breast tissue can all present in the axilla and require anatomical localisation.
Bilateral or multi-station lymphadenopathy, fever, night sweats, weight loss or hepatosplenomegaly widens the differential to haematological and systemic infectious disease.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Axillary ultrasoundFirst step - Why
- Distinguish a lymph node from a superficial or soft-tissue mass and evaluate cortical and hilar morphology.
- Interpretation and limitations
- Morphology guides sampling but is not perfectly specific; correlate with recent vaccination, infection and the breast assessment rather than using size alone.
- 02
Bilateral breast assessment - Why
- Search for a clinically occult breast primary when an unexplained node is suspicious.
- Interpretation and limitations
- Mammography and ultrasound are selected by age and context; negative breast imaging does not remove the need to establish nodal histology.
- 03
Diagnosis-directed node sampling - Why
- Obtain representative tissue from a suspicious node while preserving the material needed for carcinoma or lymphoma classification.
- Interpretation and limitations
- Breast pathways commonly use ultrasound-guided core for an abnormal node. If non-Hodgkin lymphoma is suspected, NG52 considers excision first; use core when surgical risk outweighs benefit and offer feasible excision after a nondiagnostic core.
- 04
Targeted systemic tests - Why
- Investigate infection or haematological disease when history and distribution support it.
- Interpretation and limitations
- Full blood count, inflammatory markers, microbiology or further imaging are hypothesis-driven; indiscriminate panels cannot replace tissue diagnosis for a persistent suspicious node.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Reactive lymphadenopathy
Tender nodes after vaccination, infection or skin injury may regress as the stimulus resolves, but persistence or atypical morphology requires reassessment.
Breast or nodal malignancy
Occult breast cancer, lymphoma, melanoma and metastasis from another primary enter the differential for a hard persistent node, especially with systemic or skin findings.
Superficial axillary mass
Hidradenitis, abscess, epidermal cyst, lipoma and accessory breast tissue may mimic a node; ultrasound helps localise the anatomical compartment.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked case: integrated breast assessmentApply axillary lump differential diagnosis to a defined presentationFirst stepA 62-year-old has a hard 2 cm left axillary lump, no breast symptoms and no recent vaccination or infection; breast palpation is normal.+
- 1Map the axillary lesion and examine breasts, supraclavicular areas, skin and upper limb, while asking about systemic symptoms, prior cancers, infection and immunisation.
- 2Arrange urgent breast-service assessment because an unexplained axillary lump in an adult can represent occult breast cancer or another malignancy despite normal breast palpation.
- 3Use axillary ultrasound to confirm nodal anatomy. If metastatic breast carcinoma is the leading question, obtain image-guided core; if non-Hodgkin lymphoma is plausible, coordinate with haematology and pathology and consider excision first, using core when surgical risk outweighs benefit.
- 4Complete appropriate breast imaging and let nodal histology direct any wider staging or specialist referral rather than assuming a breast origin prematurely.
- 5Verify pathology received the clinical differential and required tissue. If a risk-justified core is nondiagnostic for suspected lymphoma, offer feasible excision rather than repeating another core, then reconcile node and breast results at multidisciplinary review.
02Anatomical classificationIdentify what occupies the axillaA lump is visible or palpable in the axilla but no diagnosis has been established.+
- 1Inspect for punctum, sinus, fluctuance, accessory nipple or broad tissue fullness, then palpate whether the structure lies in skin, subcutaneous tissue or the nodal chain.
- 2Search drainage territories for breast lesion, chest-wall or upper-limb infection, melanoma and recent immunisation, while checking other nodal stations and systemic symptoms.
- 3Use ultrasound to confirm anatomy and morphology. Match sampling to the question: image-guided core for likely metastatic carcinoma, or coordinated lymphoma assessment that considers excision first and core only when its lower surgical risk justifies the trade-off.
- 4Direct the result to breast, haematology, dermatology or infection care according to the integrated evidence rather than assuming all axillary masses share one pathway.
03Node-result reconciliationResolve abnormal nodal tissue with no breast lesionCore biopsy confirms metastatic adenocarcinoma in an axillary node, but initial mammography and ultrasound show no breast primary.+
- 1Ask pathology for an immunophenotypic assessment that can support or challenge breast origin while recognising that markers are not perfectly site specific.
- 2Review breast imaging quality and consider specialist MRI when the occult-primary question remains relevant to treatment planning.
- 3AlternativeStage and discuss the case through the appropriate cancer multidisciplinary team, retaining alternative primary sites if pathology or history suggests them.
- 4Explain that the node diagnosis is established while the primary site remains under investigation, and name who will coordinate the next tests.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Missed occult primary
Assuming every axillary mass is dermatological can delay diagnosis of an imaging-occult breast cancer or another malignancy presenting first in a node.
Inappropriate node handling
Fixing all tissue in routine formalin without alerting pathology can limit lymphoma flow cytometry or microbiological analysis needed for the actual differential.
Recurrent suppuration
Hidradenitis or inadequately drained infection can recur, scar or form sinus tracts; treatment differs substantially from management of reactive lymphadenopathy.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Measure a reactive-appearing node or superficial lesion and set a defined review date after the presumed trigger, rather than advising indefinite self-observation.
- After vaccination-related lymphadenopathy, document vaccine side and date so imaging interpretation and expected resolution can be assessed accurately.
- Track sampled nodes to final histology and any required ancillary studies; inadequate material in a persistent abnormal node triggers repeat strategy.
- For treated abscess or hidradenitis, review drainage, residual mass, skin healing and recurrence because a persistent deep node may have been masked by inflammation.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Size alone is imperfect
Small nodes can be malignant and large nodes can be reactive. Cortical morphology, hilum, vascularity, distribution and clinical context guide sampling.
Vaccination is a clue, not immunity
Ipsilateral nodes after vaccination may be reactive, but an unexplained persistent or morphologically abnormal node still needs appropriate reassessment.
Accessory breast tissue is real breast tissue
It can enlarge in pregnancy, become painful cyclically and develop cysts, fibroadenoma or carcinoma; its axillary location does not make breast pathology impossible.
Plan lymphoma tissue before sampling
Core provides more architecture than cytology, but NG52 considers excision first for suspected non-Hodgkin lymphoma. Advance pathology contact also preserves fresh material for flow cytometry when required.
11Common pitfallsFrequent interpretation and management errors.
- 01
Prescribing antibiotics for every tender axillary lump can delay diagnosis when there is no cellulitis, abscess or infective source.
- 02
Assuming a normal breast examination excludes breast cancer ignores occult primaries and the limited sensitivity of palpation.
- 03
Ignoring other nodal stations and systemic symptoms can miss lymphoma or disseminated infection presenting in the axilla.
- 04
Using cytology alone or automatically choosing core for suspected lymphoma can leave inadequate architecture; follow the excision-versus-core decision with haematology and pathology before tissue is fixed.