Effocacu and Significance of Sentinel Lymph Node Identification with Technetium-99m-labeled Tin Colloids for Breast Cancer.

Abstract

PURPOSE: The sentinel lymph node (SLN) is thought to reflect the metastatic status of the remaining axillary lymph nodes in patients with breast cancer. We used technetium-99m-labeled tin colloids to identify SLN. The efficacy and significance of SLN identification using this method were investigated in terms of number, size, location, and tumor metastasis. The efficacy of the emulsion charcoalinjection method for the intraoperative visible identification of SLN was also evaluated. METHODS: Twenty-five patients with invasive breast cancer were studied. Underultrasonographic guidance, technetium-99m-labeled tin colloid particles (3 ml) were injected into 3 sites around the tumor within 3 mm of the margin or into the wall of the excisional biopsy cavity 2 hours before surgery. At surgery, just before the incision, an emulsion of charcoal particles (2.5 ml) was injected into 3 sites of the breast parenchyma surrounding the tumor. All patients underwent mastectomy with axillary dissection to the infraclavicular region. The radioactivity of each dissected lymph node was measured. All axillary specimens were processed in individual blocks for permanent section histopathologic evaluation with H & E. RESULTS: SLN were defined as lymph nodes with 100, 000 or more counts per minute (cpm) in radioactivity after injection of labeled tin colloids. In all 25 patients, SLN were identified (mean, 1.9 SLN/patient; range,1-4). Since the mean uptake in SLN was 383 124 cpm, but only 884 cpm in non-SLN nodes, discrimination between SLN and non-SLN nodes was easy. Clearly visible lymph nodes with charcoalstaining accounted for 83.3% of all SLN, although 21.3% of non-SLN also stained. SLN were located only in the axillary region, but there were no other specific features in the location or size of SLN. The SLN were metastatic in 10 of the 25 patients: in 4, the SLN were the only metastatic nodes whereas in the remaining 6 patients, other axillary nodes were also positive. Fifteen patients with no metastasis in SLN had no tumor involvement in any other lymph nodes. There were no skip metastases. CONCLUSION: SLN identified with labeled tin colloids have clinical value in predicting the metastatic status of the remaining axillary lymph nodes in breast cancer.