Intradermal isotope injection: A highly accurate method of lymphatic mapping in breast carcinoma

Background: The combined approach of radioactive tracer and blue-dye mappin g of sentinel lymph nodes (SLN) has evolved into a safe and effective alter native to routine axillary node dissection in specific patient populations with boast carcinoma. The optimal route of injection for the isotope has no t been clearly defined. To assess the intradermal route of isotope injectio n, we prospectively evaluated 100 patients with biopsy-proven invasive brea st carcinoma with SLN biopsy followed by planned axillary node dissection. Methods: All patients were given an intradermal injection of Tc-99m sulfur colloid and an intraparenchymal injection of blue dye. All patients underwe nt a complete axillary node dissection. Each sentinel node was serially sec tioned and examined by immunohistochemistry. Results: Sentinel nodes were successfully identified in 99% of cases. Forty -six patients had axillary metastases; of these, four had falsely negative sentinel nodes (false-negative rate, 9%). The false-negative rate was 0 of 24 (0%) for T1 tumors, 2 of 18 (11%) for T2 tumors, and 2 of 4 (50%) for T3 tumors. Three of four patients with false negatives had palpable, clinical ly suspicious axillary nodes found intraoperatively. If these cases are exc luded, the accuracy of the procedure was 100%;E for T1 and T2 tumors. Of th e 42 positive axillae identified by SLNB (true positives), 40 were localize d using the intradermal injection of radioisotope; in 13 of these cases, th is was the only method that identified the true-positive node. Conclusion: These data demonstrate that intradermal injection of radioactiv e tracer is an effective method of localizing the SLN in cases involving sm all breast cancers. Further investigation is warranted before this techniqu e is adopted for use in larger breast cancers. Intraoperative examination a nd biopsy of any suspicious nonsentinel nodes are critical.