How to proceed with non-FDG (Fluorodeoxyglucose) avid lesions in the left breast with non-FDG avid lymph nodes in the left axillary and internal mammary regions?

Management of Non-FDG Avid Breast Lesions with Non-FDG Avid Lymph Nodes

For non-FDG avid lesions in the left breast with non-FDG avid left axillary and internal mammary lymph nodes, proceed with conventional breast imaging workup followed by tissue sampling, as FDG-PET/CT has limited sensitivity for axillary nodal metastases and cannot reliably exclude malignancy in non-avid lesions 1.

Understanding Non-FDG Avid Lesions

Non-FDG avidity in breast lesions and associated lymph nodes does not exclude malignancy. FDG-PET/CT has several limitations in breast cancer staging:

• Limited sensitivity (48-87%) for detecting lymph node metastases despite high specificity (90-100%) 1
• Poor detection of small nodal metastases, particularly those <5mm
• Variable FDG uptake depending on tumor biology (some breast cancers, particularly low-grade or lobular carcinomas, may show minimal FDG uptake)

Recommended Diagnostic Algorithm

Step 1: Complete Breast Imaging Evaluation

• Diagnostic mammography and ultrasound of the breast lesion
• Targeted ultrasound of the axilla and internal mammary regions
• Consider breast MRI, which has superior sensitivity (82%) compared to FDG-PET/CT (64%) for nodal assessment 1

Step 2: Tissue Sampling

• Core needle biopsy of the breast lesion
• If axillary nodes appear abnormal on ultrasound (regardless of FDG avidity):
  • Perform ultrasound-guided fine needle aspiration or core biopsy of suspicious nodes
  • Consider sentinel lymph node biopsy (SLNB) if needle biopsy is negative or not feasible

Step 3: Surgical Planning Based on Pathology Results

• For malignant breast lesions:
  • Breast conservation surgery (BCS) with SLNB for clinically node-negative disease
  • Consider mastectomy with SLNB for larger tumors or when BCS is not appropriate
• For malignant axillary nodes:
  • Follow current guidelines for management of node-positive disease
  • Consider the number of positive nodes and tumor characteristics

Special Considerations for Internal Mammary Nodes

Non-FDG avid internal mammary nodes warrant attention as they may represent a separate drainage basin:

• Internal mammary nodes may be involved with or without axillary node involvement, more commonly in medial and central breast tumors 2
• Consider sampling of suspicious internal mammary nodes if it would change management
• Internal mammary node involvement may influence radiation planning decisions

Radiation Therapy Considerations

If malignancy is confirmed:

• Postoperative radiotherapy is strongly recommended after BCS 1
• For node-positive disease, nodal irradiation remains indicated 1
• Regional nodal irradiation should include the internal mammary chain if there is evidence of involvement 1

Common Pitfalls to Avoid

1. Assuming non-FDG avidity means benign disease: FDG-PET/CT has limited sensitivity for axillary staging and should not replace SLNB 1

2. Overlooking internal mammary nodes: These nodes represent an important drainage basin that can harbor metastases even with negative axillary nodes 3

3. Relying solely on FDG-PET/CT for axillary staging: SLNB remains the standard of care for axillary staging in early clinically node-negative breast cancer 1

4. False positives on FDG-PET/CT: Be aware that recent COVID-19 vaccination 4 or other immunizations 5 can cause false-positive FDG uptake in axillary nodes

5. Physiologic uptake: Conditions like breastfeeding can cause diffuse FDG avidity in breast tissue that may mask or mimic malignancy 6

By following this systematic approach, you can ensure appropriate management of non-FDG avid breast lesions and associated lymph nodes, maintaining focus on accurate diagnosis and optimal treatment planning.