Evaluation and Management of Axillary Lymphadenopathy

Initial Imaging and Diagnostic Workup

For any new palpable axillary mass, the first step is combined axillary ultrasound and diagnostic mammography (or digital breast tomosynthesis) to assess both the lymph nodes and the ipsilateral breast for an occult primary malignancy. American College of Radiology recommendation. 1
Axillary ultrasound is the cornerstone initial test because it distinguishes solid from cystic lesions and evaluates node morphology (cortical thickness, hilum integrity). American College of Radiology. 1
In women without a personal history of breast cancer who present with axillary lymphadenopathy, only about 7 % are found to have malignancy on biopsy, with prevalence increasing with age. American College of Radiology. 1

Biopsy‑indicating features (American College of Radiology):
- Complete loss of the central fatty hilum. 2
- Rounded rather than oval node shape. 2
- Increased vascularity on Doppler imaging. 3
Observation‑compatible (benign) features (American College of Radiology):
- Preserved fatty hilum. 3

Low‑risk patients (no cancer history, adenopathy ipsilateral to a recent COVID‑19 mRNA vaccine given ≤ 3 months ago) may be managed expectantly without routine follow‑up imaging. Radiology guideline. 4
High‑risk patients (known breast, head/neck, melanoma, or lymphoma) should proceed directly to tissue biopsy regardless of vaccination timing. Radiology guideline. 4
Screening mammography should be performed before vaccination or ≥ 4–6 weeks after the final vaccine dose to reduce false‑positive findings. Radiology guideline. 4

Work‑up includes axillary ultrasound (primary), diagnostic mammography/DBT, and CT chest if chest‑wall invasion is suspected. American College of Radiology. 1
If imaging shows a benign‑appearing node (e.g., lipoma or normal‑looking lymph node), no further evaluation is required. American College of Radiology. 3
Suspicious morphology on ultrasound mandates ultrasound‑guided core‑needle biopsy. American College of Radiology. 1

Differential diagnosis includes systemic diseases (lymphoma, leukemia, autoimmune disorders) [American College of Radiology]; bilateral breast cancer (rare) [American College of Radiology]; and infectious/inflammatory conditions [Radiology]. 3, 4
Initial imaging: bilateral axillary ultrasound plus diagnostic mammography. American College of Radiology. 3
If mammography is negative but nodes remain suspicious, breast MRI is recommended; it detects occult breast cancer in > ⅔ of such patients. American College of Radiology. 3

For clinically node‑negative tumors ≤ 2 cm, sentinel lymph node biopsy (SLNB) has replaced axillary lymph node dissection (ALND) as the standard staging procedure. Evidence from the Z0011 trial shows non‑inferior 10‑year overall survival with markedly lower morbidity (Level I evidence). American College of Radiology. 2, 5, 6
Pre‑operative axillary ultrasound is advised to identify patients with a higher nodal disease burden who may benefit from upfront biopsy. American College of Radiology. 2, 7
When suspicious nodes are identified on ultrasound, perform ultrasound‑guided core biopsy with marker‑clip placement. American College of Radiology. 2, 7
Routine advanced imaging (CT, PET/CT) is not indicated for asymptomatic early‑stage breast cancer because the yield for occult disease is low. American College of Radiology. 3

In node‑positive patients slated for neoadjuvant chemotherapy, a marker clip should be placed in the biopsy‑proven positive node before treatment. American College of Radiology. 8
Targeted axillary dissection (removal of the clipped node plus sentinel nodes) is preferred over complete ALND. American College of Radiology. 2
This strategy lowers the false‑negative rate to 8.4–8.7 % when ≥ 3 sentinel nodes—including the clipped node—are removed. American College of Radiology. 8, 2

Immediate tissue sampling is warranted in high‑risk situations where rapid histopathologic confirmation is needed for treatment planning (e.g., known malignancy with suspicious nodal morphology). Radiology and American College of Radiology guidelines. 4, 7

Do not delay cancer staging or treatment to await resolution of possible vaccine‑related adenopathy in patients with known or suspected malignancy. Radiology guideline. 4
Do not use FDG‑PET/CT as the initial imaging modality for an isolated axillary mass of unknown cause; it provides no diagnostic benefit. American College of Radiology. 1
Do not perform routine ALND in clinically node‑negative or limited node‑positive breast cancer; SLNB offers equivalent survival with reduced morbidity. American College of Radiology. 2, 5, 6

Clinical context can justify observation: In patients whose history provides a plausible benign explanation for axillary lymphadenopathy (e.g., recent infection or dermatologic condition), observation rather than immediate biopsy is appropriate, according to the American College of Radiology guidelines. 9

MRI as a problem‑solving tool after negative mammography: When diagnostic mammography or digital breast tomosynthesis fails to identify a primary breast lesion but the axillary nodes remain suspicious, breast MRI is recommended; it uncovers occult breast cancer in more than two‑thirds of such patients. (American College of Radiology, 2022) 9
MRI provides detailed anatomic characterization: Breast MRI not only detects hidden malignancy but also delineates the extent of axillary masses, evaluating involvement of adjacent vessels, the chest wall, and other axillary structures, thereby aiding treatment planning. (American College of Radiology, 2022) 9