What is the appropriate diagnosis and management for a patient with unilateral left axilla swelling associated with pain and febrile episodes?

Unilateral Left Axillary Swelling with Pain and Fever: Diagnosis and Management

Begin with axillary ultrasound as the initial imaging modality to differentiate between infectious/inflammatory causes and malignancy, followed by ultrasound-guided core needle biopsy for definitive diagnosis if suspicious features are identified. 1

Initial Diagnostic Approach

Clinical Assessment

The combination of unilateral axillary swelling, pain, and fever significantly narrows the differential diagnosis toward acute infectious or inflammatory processes, though malignancy with inflammatory features must be excluded. 1 The presence of hyperemia (implied by pain and fever) suggests an acute process requiring prompt evaluation. 1

Key differential diagnoses include:

• Infectious causes: Reactive lymphadenopathy from bacterial or viral infections (most common benign etiology) 2, 1
• Malignant causes: Metastatic breast cancer (most common when malignancy is confirmed), lymphoma, or occult breast primary 2, 1
• Inflammatory conditions: Autoimmune diseases or dermatopathic lymphadenopathy 2

Initial Imaging Strategy

Axillary ultrasound is the most appropriate first-line imaging test for any palpable axillary mass, including those with pain and fever. 3, 1 This modality allows assessment of:

• Whether the mass is solid or cystic 1
• Lymph node morphology (presence or absence of fatty hilum) 1
• Surrounding soft tissue inflammation 1
• Vascular flow patterns 1

For patients ≥30 years of age, add diagnostic mammography and/or digital breast tomosynthesis to complement axillary ultrasound and evaluate for an occult breast primary lesion. 1 However, mammography should never be performed alone without ultrasound, as it has a high false-negative rate for detecting axillary lymphadenopathy. 1

Critical Imaging Pitfalls to Avoid

• Do not assume hyperemia automatically indicates benign disease—malignancy can present with overlying skin changes. 1
• Do not rely on negative ultrasound alone to exclude malignancy—axillary ultrasound has relatively low negative predictive value and sensitivity. 1
• Do not delay biopsy if imaging shows suspicious features—absence of fatty hilum has 90-93% positive predictive value for malignancy. 1

Tissue Diagnosis

Perform ultrasound-guided core needle biopsy rather than fine needle aspiration if ultrasound demonstrates suspicious features or if clinical concern persists despite benign-appearing imaging. 1 Core biopsy is superior because:

• Sensitivity: 88% vs. 74% for FNA 1
• Specificity: 98-100% for both modalities 1
• Provides architectural information crucial for distinguishing reactive lymphadenopathy from lymphoma 1
• Allows immunohistochemical studies 1

Note: If lymphoma is suspected based on imaging or clinical presentation, special pathologic evaluation and/or surgical excision may be required rather than core biopsy alone. 1

Management Based on Biopsy Results

If Benign/Reactive Lymphadenopathy

• Treat the underlying infection or inflammatory condition with appropriate antibiotics or anti-inflammatory therapy 1
• Consider short-interval follow-up ultrasound (typically 4-6 weeks) to document resolution 1

If Malignancy of Breast Origin

• Proceed with breast MRI if mammography/ultrasound shows no breast primary 1
• MRI helps define disease extent and characterize the breast primary when axillary ultrasound reveals adenopathy of unknown primary malignancy 3
• Follow NCCN Guidelines for Breast Cancer management 1

If Lymphoma or Other Hematologic Malignancy

• Non-Hodgkin's lymphoma frequently presents with nodal involvement and requires definitive diagnosis through biopsy rather than observation alone 2
• Consider CT chest, abdomen, and pelvis if systemic disease or lymphoma is in the differential to determine other areas of lymphadenopathy and assess for local involvement 3

Additional Diagnostic Considerations

Do not routinely order FDG-PET/CT as initial imaging—it is not beneficial for assessing an axillary mass of unknown etiology because of its low yield to detect an occult primary malignancy without first confirming malignant etiology. 3 Less than 1% of breast cancers initially present as axillary adenopathy. 3

Bilateral vs. Unilateral Distinction: The unilateral presentation in this case makes systemic processes (infections, inflammatory conditions, hematologic malignancies) less likely than localized infectious or malignant causes. 2 Bilateral axillary lymphadenopathy would more commonly suggest systemic processes. 2