A validation trial of subdermal injection compared with intraparenchymal injection for sentinel lymph node biopsy in breast cancer

Sentinel lymph node (SLN) biopsy is increasingly being used as an accurate and less morbid surrogate for axillary dissection. However, a standardized technique in the biopsy of SLNs is not used. Some authors propose subdermal injection to be as accurate as peritumoral intraparenchymal injection (IPI). Our objective is to determine whether the SLNs identified by subdermal injection truly represent SLNs and match those found with IPI. Specific end points of the study were 1) successful localization of the SLN by the IPI of isosulfan blue or the radiocolloid intradermal injection, 2) successful uptake of radiocolloid and isosulfan blue on individual SLN, and 3) determination of the frequency with which the radiocolloid injection detected the "gold standard" blue SLN. SLNs were found in 71 of 73 cases (success rate = 97%). Blue SLNs were identified in 64 patients (88%). SLNs in 61 patients (84%) were radioactive. A total of 112 SLNs were identified in 71 patients (1.6 nodes/patient). Seventy-six of 87 SLNs found with IPI were also radioactive (concordance of 87%). All SLNs harboring metastatic cancer (16 patients) were found by both techniques, being both blue and radioactive. Our results support the concept of shared lymphatic pathways in the breast with a high degree of communication between the subdermal lymphatics and the intraparenchymal lymphatics. The success in identification of the SLN is made simpler and improved by the addition of subdermal radiocolloid injection.