What is the diagnosis and management for a 41-year-old female with throbbing pain under the left rib cage and left chest/breast, accompanied by swollen left axilla (axillary) lymph nodes for over six months?

Differential Diagnosis and Management of Left-Sided Chest Pain with Chronic Axillary Lymphadenopathy

This 41-year-old woman requires immediate diagnostic mammography and axillary ultrasound at the same visit to rule out occult breast cancer, which is the most common malignant cause of unilateral axillary lymphadenopathy in women of this age. 1, 2

Immediate Diagnostic Workup

Begin with diagnostic mammography (including standard views plus magnification views to detect microcalcifications) followed immediately by targeted axillary ultrasound at the same visit. 2 This age-stratified approach is mandatory for women ≥30 years according to the American College of Radiology. 2

Key Imaging Sequence:

• Complete all imaging studies before any tissue biopsy, as biopsy-related changes will confound subsequent image interpretation. 2
• Axillary ultrasound determines whether the lymph nodes are solid or cystic and characterizes their morphology. 3, 2
• If mammography and ultrasound show no breast primary but lymph nodes appear suspicious, proceed to breast MRI, which identifies occult breast cancer in approximately 70% of patients with suspicious axillary lymphadenopathy and negative conventional imaging. 3, 2

Differential Diagnosis Considerations

Malignant Causes (Most Critical):

• Occult breast cancer is the leading concern when cancer is confirmed in axillary nodes, even when initial imaging shows no breast abnormality. 1, 4
• Metastatic adenocarcinoma from breast origin can present with isolated axillary masses—in one series, 9 of 17 cancer cases had occult breast cancer, with 5 in the contralateral breast. 1, 4
• Lymphoma (particularly non-Hodgkin's) should be considered, though unilateral presentation is less typical than bilateral involvement. 4

Benign/Infectious Causes:

• Reactive lymphadenopathy from mastitis or cellulitis of the breast, arm, or chest can cause axillary swelling. 1, 4
• Granulomatous inflammation is a possible benign etiology. 1
• Breast implant-related lymphadenopathy (if patient has implants). 1

Critical Clinical Context:

The six-month duration of lymphadenopathy is concerning and argues strongly against simple reactive adenopathy, which typically resolves within weeks to months. 1 Unilateral presentation favors breast cancer over systemic processes like lymphoma, which more commonly presents bilaterally. 2, 4

Tissue Diagnosis Protocol

If imaging shows suspicious lymph nodes, proceed with core needle biopsy (preferred over fine needle aspiration) of the axillary mass. 3, 2

• Consult pathology to ensure adequate tissue for immunohistochemical staining, including ER/PR and HER2 status if adenocarcinoma is identified. 3
• Elevated ER/PR levels provide strong evidence for breast cancer diagnosis. 3

Additional Diagnostic Considerations

Assess for systemic disease or other sites of adenopathy through complete clinical evaluation. 1 This includes:

• Physical examination of all nodal basins
• Assessment for B symptoms (fever, night sweats, weight loss) suggesting lymphoma
• History of recent infections, autoimmune disease, or breast implants 1, 4

Advanced imaging with FDG-PET/CT should be reserved for specific indications, such as when lymphoma is suspected or to evaluate for distant metastases if breast cancer is confirmed. 3 PET/CT can detect axillary and other lymphadenopathy throughout the body, though it has limited sensitivity (54%) for axillary metastases. 3

Management Based on Findings

If Breast Cancer is Confirmed:

For clinically node-negative breast cancer ≤2 cm, sentinel lymph node biopsy (SLNB) has replaced axillary lymph node dissection (ALND) as standard of care, with non-inferior 10-year overall survival. 2 However, this patient's palpable six-month lymphadenopathy likely represents clinically node-positive disease, which may require different surgical management.

If No Primary is Identified:

Breast MRI is mandatory to identify occult primary, as it detects breast cancer in more than two-thirds of patients with suspicious axillary lymphadenopathy and negative conventional imaging. 3, 2

Critical Pitfalls to Avoid

• Never rely on physical examination alone, as both sensitivity and specificity are limited for assessing axillary disease. 2
• Do not delay biopsy of suspicious nodes, as early diagnosis significantly impacts treatment planning and prognosis. 2
• Do not assume benign etiology despite the positional nature of pain—the six-month duration demands definitive diagnosis. 1
• Do not perform exhaustive systemic workup before completing breast-directed evaluation, as breast cancer is the most common malignant cause of unilateral axillary adenopathy in this demographic. 1, 4

Regarding the Positional Pain

The throbbing pain with position changes and bending forward may represent musculoskeletal chest wall pain or costochondritis, but this symptom pattern does not exclude underlying malignancy and should not delay the cancer workup. The pain could also represent referred pain from axillary lymphadenopathy or breast pathology. Complete the diagnostic imaging and tissue diagnosis first before attributing symptoms to benign musculoskeletal causes.