Sentinel lymph node biopsy using tin colloid RI and blue dye method

Axillary dissection has been considered essential for breast cancer staging because nodal metastasis is the most powerful predictive factor for recurrence. On the other hand, morbidity, such as lymphedema and shoulder dysfunction, may occur. Sentinel node biopsy is a good way to avoid unnecessary axillary dissection. We used tin colloid as a carrier of Tc99m tracer together with the blue dye method. The detection rate of the sentinel node was 27 cases out of 29 (90%) for the blue dye method, 10 cases out of 19 (53%) for the RI method, and 27 out of 33 (82%) for the combined method. The detection rate of the RI method was improved after adding the subcutaneous injection over the tumor from 45% before adding the subcutaneous injection to 82% after adding it. The false negative rate was 11% for the blue dye method, 0% for the RI method, and 10% for the combined method. This yields a sensitivity of 89% for the blue dye method, 100% for the RI method, and 90% for the combined method. Specificity was 100% for all three methods. Accuracy was 96% for the blue dye method, 100% for the RI method, and 96% for the combined method. There were two false negative cases. The average number of sentinel lymph nodes was 2.12 for the dye method, 1.66 for the RI method, and 1.95 for the combined method. There were three of 49 cases with identified parasternal lymph nodes by RI imaging. Lymphatic mapping using tin colloid may be useful for detecting sentinel nodes.