Carbon Suspension vs. Metallic Marker for Axillary Lymph Node Marking in Breast Cancer After Neoadjuvant Therapy

Under ultrasound guidance, 0.5 mL of sterile carbon particle suspension (Black Eye) is injected into the capsule of the metastatic axillary lymph node(s). Technique: Performed using a high-frequency linear ultrasound probe (e.g., 12 MHz) and a 22G needle. Target: Up to 3 pathologically confirmed metastatic lymph nodes. Timing: Performed before initiation of neoadjuvant systemic therapy (NST). Rationale: Carbon suspension provides long-term visual localization due to its black staining properties. Inert and biocompatible, with minimal risk of allergic reactions. Patients proceed to standard NST based on tumor subtype (chemotherapy, targeted therapy, or endocrine therapy). Post-NST imaging (ultrasound, CT, or PET-CT) to assess treatment response. Surgical Intervention: Targeted axillary dissection (TAD) with removal of marked nodes + sentinel lymph node biopsy (SLNB) using fluorescent dye. Intraoperative frozen section analysis (hematoxylin \& eosin staining) of excised nodes.

A 4-mm nitinol (nickel-titanium alloy) marker (TWIRL ULTRACOR) is deployed into the metastatic lymph node(s) under ultrasound guidance. Technique: Uses a specialized introducer kit for precise placement. Target: Up to 3 pathologically confirmed metastatic lymph nodes. Timing: Performed before initiation of NST. Rationale: Nitinol markers are radiopaque, MRI-compatible, and resistant to migration. Standard method for tumor localization in breast cancer. Post-Marking Protocol: Identical NST and imaging follow-up as Group 1. Surgical Intervention: TAD with marker localization (palpation/imaging-guided excision) + SLNB. Intraoperative frozen section analysis.