Evaluation of mammary lymphoscintigraphy by a single intratumoral injection for sentinel node identification

The aim of this study was to evaluate the findings of mammary lymphoscintig raphy by a single intratumoral injection in 150 patients with breast carcin oma: 100 patients (group A) investigated in the validation phase of the stu dy and 50 (group B) studied after the tracer dose was optimized. Methods: i mmediately after injection of Tc-99m-nanocolloid using a 25-gauge needle an d a 0.2-mL volume, simultaneous anterior and lateral images were acquired w ith a dual-head gamma camera during 20 min followed by sequential static an terior and prone lateral breast images after 30 min and after 2 and 4 h. Co -57-assisted skin marking defined the sentinel node location for subsequent gamma probe, blue dye-guided sentinel node biopsy. Results: In group A (me an dose, 61.6 MBq; range, 42-88 MBq) scintigraphy revealed lymph nodes in 8 3 patients (83%), with an increase in the rate of visualization from 72% fo r the first 40 patients to 90% for the last 60; patient age (P = 0.01) and administered tracer dose (P = 0.04) were found to be significant factors fo r visualization, with optimal results obtained from doses higher than 65 MB q. Lymph nodes were visible in 34 patients (41%) during the first 30 min af ter injection, whereas in 49 patients appearance occurred at 2-4 h. A total of 97 lymphatic basins were visualized (80 axillary, 3 clavicular, 14 inte rnal mammary). in group B (mean dose, 90.8 MBq; range, 68-124 MBq), the Vis ualization rate was 94%, with early lymph node appearance in 27 patients (5 7%) and a total of 53 basins (45 axillary, 8 internal mammary). In combinat ion with intraoperative blue dye mapping and gamma probing, the identificat ion rate increased to 90% in group A and 98% in group B. Prone lateral imag es contributed to identification of intramammary lymph nodes in a total of 14 patients and axillary nodes close to the injection site in 8 other patie nts. Conclusion: Mammary lymphoscintigraphy by single intratumoral injectio n is a valid method for lymphatic mapping and identification of both axilla ry and nonaxillary sentinel nodes. Lymph node Visualization appears to be i mproved with higher tracer doses. The compactness of the injection site ena bles high-quality additional lateral images that can depict intramammary or axillary lymph nodes adjacent to the injection site.