What is the appropriate evaluation and management of a woman with an axillary lump?

Evaluation and Management of Axillary Lump in Women

Initial Imaging Approach

Axillary ultrasound is the single most appropriate initial imaging test for any woman presenting with a palpable axillary lump, regardless of whether it is unilateral or bilateral. 1, 2

Age-Stratified Imaging Protocol

• For women ≥30 years old: Perform diagnostic mammography (or digital breast tomosynthesis) plus axillary ultrasound at the same visit to evaluate for an occult breast primary lesion. 1, 2, 3

• For women <30 years old: Begin with targeted axillary ultrasound alone to avoid unnecessary radiation exposure in this lower-risk age group. 3

• The mammogram serves a critical function beyond evaluating the palpable lump—it identifies occult breast cancer in the ipsilateral or contralateral breast that may have metastasized to the axilla, detects synchronous cancers, and reveals microcalcifications indicating ductal carcinoma in situ. 3

Understanding the Differential Diagnosis

Unilateral Axillary Lump

The differential is broad but can be systematically approached:

• Benign causes (most common): Reactive lymphadenopathy from infection, inflammatory disease, autoimmune conditions, nerve sheath tumors, accessory breast tissue lesions (fibroadenoma, fibrocystic changes), lipomas, and epidermal inclusion cysts. 1, 4, 5, 6, 7

• Malignant causes: Metastatic breast cancer (including occult primary presenting as isolated axillary adenopathy in <1% of cases), lymphoma, and metastases from non-breast malignancies. 1, 4, 8

• Critical context: In women with no personal history of breast cancer, only 7% of abnormal axillary nodes biopsied prove malignant, but this risk increases with age. 1

Bilateral Axillary Lumps

• More likely systemic processes: Reactive lymphadenopathy from infections, inflammatory conditions, autoimmune diseases, lymphoma, or leukemia. 1, 4

• Silicone adenitis: Ruptured breast implants can cause bilateral axillary adenopathy with a characteristic "snowstorm" ultrasound appearance and may show FDG uptake on PET/CT, mimicking malignancy. 4

Ultrasound Interpretation and Biopsy Indications

Suspicious Ultrasound Features

Perform ultrasound-guided core needle biopsy (not fine needle aspiration) when any of the following features are present:

• Short-axis diameter >1 cm 1
• Cortical thickness >0.3 cm 1
• Absence of fatty hilum (highest positive predictive value of 90-93% for malignancy) 1, 2
• Hard, matted, or fixed nodes on clinical examination 4

Why Core Biopsy Over FNA

• Core needle biopsy provides superior diagnostic accuracy with sensitivity of 88% and specificity of 98-100%, compared to FNA sensitivity of 74%. 2

• Core biopsy yields architectural information essential for distinguishing reactive lymphadenopathy from lymphoma and allows immunohistochemical studies. 2

Critical Pitfalls to Avoid

• Never assume hyperemia or inflammatory features automatically indicate benign disease—malignancy can present with overlying skin changes. 2

• Do not rely on negative ultrasound alone to exclude malignancy—axillary ultrasound has relatively low negative predictive value and sensitivity (26-94% sensitivity, 53-98% specificity). 1, 2

• Never perform mammography alone without ultrasound—mammography has a high false-negative rate for detecting axillary lymphadenopathy. 1, 2

• Avoid empiric antibiotics before imaging when clinical suspicion is high, as this delays identification of inflammatory breast cancer or other malignancies. 4

• Complete all imaging before tissue diagnosis—biopsy-related changes confuse subsequent image interpretation. 3

• Recognize the "snowstorm" ultrasound pattern as diagnostic for silicone adenitis and evaluate for implant rupture rather than pursuing malignancy workup. 4

Management Based on Findings

If Imaging Shows Suspicious Features

• Proceed directly to ultrasound-guided core needle biopsy. 2, 3

• If biopsy confirms malignancy of breast origin but mammography/ultrasound show no breast primary, breast MRI is mandatory—it reveals occult breast cancer in approximately 70% of such cases. 4, 3

If Imaging Appears Benign

• For benign/reactive lymphadenopathy: Treat underlying infection or inflammatory condition and perform short-interval follow-up ultrasound to document resolution. 2

• For nodes >2 cm, hard, or matted despite benign imaging (BI-RADS 1-3), do not delay tissue diagnosis when clinical suspicion is high. 4

Role of Advanced Imaging

• FDG-PET/CT is not beneficial as initial imaging for an axillary mass of unknown etiology because of low yield to detect occult primary malignancy without first confirming malignant etiology. 1

• CT chest may be helpful if chest wall invasion is suspected or if systemic disease (lymphoma) is in the differential to assess for other lymphadenopathy and local involvement. 1

• Breast MRI is reserved for defining disease extent when ultrasound reveals adenopathy of unknown primary and mammogram is negative, or for characterizing chest wall involvement. 1