What are the possible causes and recommended evaluation and treatment for lateral breast pain radiating to the axilla?

Lateral Breast Pain Radiating to Axilla

For lateral breast pain extending to the axilla, you must obtain diagnostic mammography (if age ≥40) followed by targeted ultrasound of the painful area and axilla to exclude underlying pathology, particularly given that 10-15% of extramammary causes (musculoskeletal, nerve entrapment, or chest wall conditions) can mimic breast pain, and focal tenderness mandates imaging evaluation. 1, 2

Initial Clinical Assessment

Document these specific features:

• Pain pattern: Cyclical (hormonal, menstrual-related) versus noncyclical (constant, unrelated to menses) 1
• Exact location: Lateral breast tissue versus chest wall versus axillary tail of breast 1
• Reproducibility: Can you reproduce the pain with palpation? Does it worsen with arm movement or deep breathing? 1
• Associated findings: Palpable mass, skin changes (erythema, dimpling), nipple discharge, or axillary lymphadenopathy 2, 3
• Red flags: Unilateral focal pain, age >40, persistent pain >3 months, or any palpable abnormality 1, 2

Differential Diagnosis by Location

True breast causes (lateral breast tissue):

• Breast cyst causing focal pain 2, 3
• Duct ectasia with periductal inflammation (burning pain, often in smokers) 1
• Mondor disease (thrombophlebitis of thoracoepigastric vein) 1
• Breast cancer (1.2-6.7% risk with pain alone, but higher with focal tenderness) 2, 3

Extramammary causes (10-15% of "breast pain"):

• Musculoskeletal: Pectoral muscle strain/spasm, intercostal muscle pain, rib fracture 1
• Nerve entrapment: Lateral cutaneous branch of third intercostal nerve 1
• Chest wall: Costochondritis (Tietze syndrome), fibromyositis 1
• Cervical/thoracic spine: Nerve root syndrome radiating to lateral chest 1

Axillary causes:

• Reactive lymphadenopathy (infection, inflammation) 1, 4
• Accessory breast tissue in axilla 1, 4
• Metastatic breast cancer to axillary nodes 1, 4
• Lymphoma 1, 4

Imaging Algorithm

Age ≥40 years:

1. Diagnostic mammography (ACR rating 4/9 for noncyclical pain) 1, 2
2. Targeted ultrasound of the tender area and axilla (ACR rating 9/9 for palpable findings) 2, 5
3. Ultrasound of axilla to evaluate lymph nodes if axillary component present 1, 6

Age <40 years:

1. Ultrasound alone of breast and axilla as initial study 3, 7
2. Reserve mammography only for highly suspicious clinical findings 3, 7

Critical pitfall: Never dismiss a palpable clinical finding based solely on negative mammography—10-15% of breast cancers are mammographically occult, and ultrasound may detect lesions not visible on mammography. 5

Management Based on Imaging Results

BI-RADS 1 (Negative) or BI-RADS 2 (Benign):

• Symptomatic management: NSAIDs, acetaminophen, supportive bra, ice/heat 2, 3
• Reassurance alone resolves symptoms in 52% of women with severe pain 2
• If pain persists and musculoskeletal cause suspected: physical therapy, stretching exercises 1

BI-RADS 3 (Probably Benign - e.g., complicated cyst):

• Short-interval ultrasound follow-up every 6 months for 1-2 years (ACR rating 8/9) 2, 3
• Consider cyst aspiration if geographically correlated with pain for symptom relief 2, 3

BI-RADS 4 or 5 (Suspicious or Highly Suggestive of Malignancy):

• Core needle biopsy immediately (ACR rating 9/9) 2, 3, 5
• Do not delay tissue diagnosis 3

Negative imaging but persistent focal pain:

• Consider MRI if clinical suspicion remains high, though generally rated "usually not appropriate" (ACR rating 2/9) in standard algorithms 5
• Evaluate for musculoskeletal causes: trial of physical therapy, assess for reproducible chest wall tenderness 1

Specific Treatment Considerations

For musculoskeletal/chest wall pain:

• First-line: Acetaminophen or NSAIDs 1, 2
• Physical therapy with stretching exercises 1
• Topical NSAIDs if oral medications fail 7

For nerve-related pain:

• Consider duloxetine (SNRI) for neuropathic pain: start 30 mg daily × 1 week, then increase to 60 mg daily (30-50% pain reduction) 1

For persistent severe pain resistant to conservative measures:

• Refer to breast specialist or pain management 1, 7
• Consider acupuncture (shown effective in multiple trials) 1

Key Clinical Pearls

• Focal pain + lateral location + axillary radiation = mandatory imaging workup, regardless of age, as this differs fundamentally from diffuse breast pain where cancer risk is only 1.2-6.7% 2, 3
• The nerve supply to the breast is from intercostal nerves T3-T5, and irritation anywhere along their course can cause lateral breast or axillary pain 1
• Inflammatory breast cancer can present with pain, tenderness, and skin changes—always assess skin for erythema, warmth, or peau d'orange 1, 3
• Pain that worsens with arm movement or deep breathing suggests musculoskeletal or chest wall origin rather than true breast pathology 1
• Never initiate antibiotics for suspected mastitis before obtaining diagnostic imaging, as this can delay diagnosis of inflammatory breast cancer 3