Internal Mammary Sentinel Lymph Node Biopsy With Modified Injection Technique: High Visualization Rate and Accurate Staging

Although the 2009 American Joint Committee on Cancer incorporated the internal mammary sentinel lymph node biopsy (IM-SLNB) concept, there has been little change in surgical practice patterns because of the low visualization rate of internal mammary sentinel lymph nodes (IMSLN) with the traditional radiotracer injection technique. In this study, various injection techniques were evaluated in term of the IMSLN visualization rate, and the impact of IM-SLNB on the diagnostic and prognostic value were analyzed. Clinically, axillary lymph nodes (ALN) negative patients (n = 407) were divided into group A (traditional peritumoral intraparenchymal injection) and group B (modified periareolar intraparenchymal injection). Group B was then separated into group B1 (low volume) and group B2 (high volume) according to the injection volume. Clinically, ALN-positive patients (n = 63) were managed as group B2. Internal mammary sentinel lymph node biopsy was performed for patients with IMSLN visualized. The IMSLN visualization rate was significantly higher in group B than that in group A (71.1% versus 15.5%, P < 0.001), whereas the axillary sentinel lymph nodes were reliably identified in both groups (98.9% versus 98.3%, P = 0.712). With high injection volume, group B2 was found to have higher IMSLN visualization rate than group B1 (75.1% versus 45.8%, P < 0.001). The IMSLN metastasis rate was only 8.1% (12/149) in clinically ALN-negative patients with successful IM-SLNB, and adjuvant treatment was altered in a small proportion. The IMSLN visualization rate was 69.8% (44/63) in clinically ALN-positive patients with the IMSLN metastasis rate up to 20.5% (9/44), and individual radiotherapy strategy could be guided with the IM-SLNB results. The modified injection technique (periareolar intraparenchymal, high volume, and ultrasound guidance) significantly improved the IMSLN visualization rate, making the routine IM-SLNB possible in daily practice. Internal mammary sentinel lymph node biopsy could provide individual minimally invasive staging, prognosis, and decision making of the internal mammary radiotherapy, especially for clinically ALN-positive patients.