Background: Sentinel lymph node (SLN) biopsy is fast becoming the standard for testing lymph node involvement in many institutions. However, questions remain as to the best method of injection. The authors hypothesized that a subareolar injection of material would drain to the same lymph node as a peritumoral injection, regardless of the location of the tumor. Methods: To test this theory, 68 patients with 69 operable invasive breast carcinomas and clinically node-negative disease were enrolled in this single-institution Institutional Review Board-approved trial. Patients were injected with 1.0 mCi of technetium-99 sulfur colloid (unfiltered) in the subareolar area of the tumor-bearing breast. Each patient received an injection of 2 to 5 cc of isosulfan blue around the tumor. Radioactive SLNs were identified using a hand-held gamma detector probe. Results: The average age of patients entered into this trial was 55.2 ± 13.4 years. The average size of the tumors was 1.48 ± 1.0 cm. Thirty-two percent of the patients had undergone previous excisional breast biopsies. Of the 69 lesions, 62 (89.9%) had SLNs located with the blue dye and 65 (94.2%)with the technetium. In four patients, the SLN was not located with either method. All blue SLNs were also radioactive. All located SLNs were in the axilla. Of the 62 patients in which the SLNs were located with both methods, an average of 1.5 ± 0.7 SLNs were found per patient, of which 23.2% had metastatic disease. All four patients in which no SLN was located with either method had undergone prior excisional biopsies. Conclusions: The results of this study suggest that subareolar injection of technetium is as accurate as peritumoral injection of blue dye. Central injection is easy and avoids the necessity for image-guided injection of nonpalpable breast lesions. Finally, subareolar injection of technetium avoids the problem of overlap of the radioactive zone of diffusion of the injection site with the radioactive sentinel lymph node, particularly in medial and upper outer quadrant lesions.
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