What are the possible causes of waxing and waning axillary lymphadenopathy in a female?

Causes of Waxing and Waning Axillary Lymphadenopathy in Females

Waxing and waning axillary lymphadenopathy in females is most commonly caused by benign reactive processes—including infectious, inflammatory, and autoimmune conditions—but requires systematic evaluation to exclude malignancy, particularly lymphoma, which can present with fluctuating adenopathy. 1, 2

Benign Causes

Infectious and Inflammatory Etiologies

• Nonspecific reactive lymphadenopathy is the single most common cause, accounting for 29% of axillary lymphadenopathy cases in females 3
• Kikuchi-Fujimoto disease (histiocytic necrotizing lymphadenitis) can mimic malignant lymphoma with fluctuating axillary nodes and should be differentiated histologically 4
• Acute infections and granulomatous disease (healed or active) produce transient or fluctuating adenopathy 5
• Collagen vascular diseases (rheumatoid arthritis, lupus) cause reactive adenopathy that may wax and wane with disease activity 3

Vaccine-Related Adenopathy

• COVID-19 vaccination causes axillary lymphadenopathy in 0.3–53% of recipients, with an average duration exceeding 100 days and documented persistence up to 12 weeks 6, 7
• Seasonal influenza and other vaccines also produce axillary adenopathy, though systematic data are limited 6
• Adenopathy ipsilateral to the vaccination site that fluctuates over weeks to months is characteristic 7

Malignant Causes

Hematologic Malignancies

• Lymphoma (both Hodgkin and non-Hodgkin) commonly presents with waxing and waning lymphadenopathy; composite lymphoma (coexistence of two lymphoma types) is a rare but documented cause of fluctuating cervical and axillary nodes 2
• Chronic lymphocytic leukemia or well-differentiated lymphocytic lymphoma accounts for 17% of axillary lymphadenopathy cases 3
• Non-Hodgkin lymphoma represents 6 of 21 malignant cases (29%) in patients with isolated axillary adenopathy on screening 5

Metastatic Disease

• Metastatic breast cancer accounts for 26% of axillary lymphadenopathy; less than 1% of breast cancers initially present as isolated axillary adenopathy 1, 3
• Metastatic disease from non-breast primaries (melanoma, head/neck cancer) or unknown primary sites can produce fluctuating adenopathy 3, 5

Bilateral Adenopathy Differential

• Bilateral axillary lymphadenopathy suggests systemic disease: lymphoma, leukemia, autoimmune disorders, or bilateral breast cancer (rare) 1, 8

Diagnostic Approach

Initial Imaging

• Axillary ultrasound is the cornerstone initial test to evaluate node morphology (cortical thickness, hilum integrity, shape, vascularity) 1, 8
• Diagnostic mammography or digital breast tomosynthesis should be performed concurrently to assess for occult breast primary 8

Sonographic Features Requiring Biopsy

• Complete loss of fatty hilum, rounded (not oval) shape, increased Doppler vascularity, or ill-defined/spiculated margins mandate ultrasound-guided core biopsy 8, 3
• Nodes >33 mm in length have 97% specificity for malignancy 3

Management Based on Vaccination History

• Low-risk patients (no cancer history, adenopathy ipsilateral to COVID-19 vaccine within 12 weeks, no suspicious breast findings) should be classified as benign (BI-RADS 2) with no further workup 8, 7
• High-risk patients (known breast, melanoma, lymphoma, or head/neck cancer) require immediate tissue biopsy regardless of vaccination timing 8
• If adenopathy persists >3 months post-vaccination, perform sonographic follow-up at 6 months; biopsy persistent, progressive, or morphologically suspicious nodes 6

When to Biopsy Immediately

• Any patient with known or suspected malignancy should undergo immediate biopsy without delay for possible vaccine-related adenopathy 8, 6
• Suspicious morphology on ultrasound (loss of hilum, rounded shape, abnormal vascularity) warrants ultrasound-guided core biopsy even in low-risk patients 8
• Bilateral adenopathy with negative mammography should prompt breast MRI (detects occult cancer in >67% of such cases) followed by biopsy if nodes remain suspicious 8

Critical Pitfalls to Avoid

• Do not delay cancer staging or treatment to await resolution of possible vaccine-related adenopathy in patients with known or suspected malignancy 8, 6
• Do not assume all fluctuating adenopathy is benign; composite lymphoma and other hematologic malignancies can present with waxing and waning nodes 2
• Do not use FDG-PET/CT as initial imaging for isolated axillary mass of unknown etiology; it provides no diagnostic benefit over ultrasound 1, 8
• Do not rely solely on size criteria; morphologic features (hilum loss, shape, margins) are more predictive of malignancy than absolute size 8, 3