Causes of Left Axillary and Left Breast Lymphadenitis
Primary Diagnostic Consideration
When cancer is identified in axillary lymph nodes, breast cancer is the most common cause of axillary lymphadenopathy, though localized axillary masses are more often related to benign disorders than malignancy. 1
Malignant Causes
Breast Cancer (Most Common Malignant Cause)
- Ipsilateral breast cancer is the leading malignant cause when cancer is confirmed in axillary nodes 1
- Occult breast cancer can present with isolated axillary masses—in one study, 9 of 17 cancer cases had occult breast cancer, with 5 in the contralateral breast 1
- Metastatic adenocarcinoma from breast origin may be present even when initial ultrasound and mammography show no breast abnormality 1
Other Malignancies
- Non-Hodgkin lymphoma (second most common malignancy in suspicious axillary nodes with normal breast imaging) 2
- Malignant melanoma 2
- Metastases from lower genital tract 2
Benign/Infectious Causes
Infections and Inflammation
- Specific infectious diseases including tuberculosis (found in 4 of 33 benign cases in one series) 2
- Generalized infectious disease patterns 2
- Cellulitis of the breast, arm, or chest (particularly in patients with pre-existing lymphedema) 1
- Rhodococcus species infection (rare but documented) 3
Accessory Breast Tissue Pathology
- Fibroadenoma in axillary accessory breast tissue 4
- Lactational changes in accessory breast tissue 4
- Carcinoma arising in accessory breast tissue 5
Other Benign Causes
- Reactive lymphadenopathy from mastitis 1
- Granulomas 1
- Breast implant-related benign axillary lymphadenopathy 1
- Post-surgical complications (seroma, lymphocele, hematoma) 5
- Soft tissue tumors (hemangioma, lymphangioma, peripheral nerve sheath tumors, lipomas) 5
Treatment-Related Lymphedema Causes
Secondary Lymphedema (Not Infection, But Swelling)
- Axillary lymph node dissection for breast cancer (30-50% risk) 6
- Radiation therapy to supraclavicular lymph nodes or axilla 1, 6
- Combined surgery and radiation creates additive risk 6
- May develop immediately after treatment or years later (up to 11-30 years post-treatment) 6, 7
Diagnostic Algorithm
Initial Clinical Evaluation
- Complete clinical evaluation to assess for other sites of adenopathy and potential non-breast etiologies 1
- Assess for signs of systemic disease or lymphoma 1
- Evaluate for history of breast cancer treatment, breast implants, or recent infections 1
Age-Appropriate Imaging
- For patients ≥30 years: ultrasound with mammogram 1
- For patients <30 years: ultrasound alone 1
- MRI if core needle biopsy shows malignancy of breast origin but ultrasound/mammogram negative for breast abnormality 1
Tissue Diagnosis
- Core needle biopsy recommended for palpable axillary mass that is suspicious or highly suggestive on imaging 1
- Suspicion of lymphoma may require special pathologic evaluation and/or surgical excision 1
- Fine needle aspiration and/or core needle biopsy are sufficient methods for clarification in the majority of cases 2
Ultrasound Features Predicting Malignancy
- Diffuse cortical thickening and complete loss of echo texture are the only features predicting malignancy 2
- Palpation and mean size of lymph nodes have no predictive value for malignancy 2
Critical Clinical Pitfalls
- Do not assume all axillary lymphadenopathy is breast cancer—only 1 of 18 malignant cases in one series was occult breast cancer, while 11 were lymphomas 2
- Suspicious lymph nodes with normal breast imaging rarely indicate occult breast cancer but show a variety of other malignancies and generalized infectious diseases 2
- Accessory breast tissue in the axilla can undergo the same pathological processes as normal breast tissue, including fibroadenoma and carcinoma 4
- If cellulitis develops in a patient with lymphedema, treat promptly with antibiotics as it can significantly exacerbate lymphedema 1, 7