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 lymphoscintigraphy by a single intratumoral injection in 150 patients with breast carcinoma: 100 patients (group A) investigated in the validation phase of the study and 50 (group B) studied after the tracer dose was optimized.

Immediately after injection of 99mTc-nanocolloid using a 25-gauge needle and a 0.2-mL volume, simultaneous anterior and lateral images were acquired with a dual-head gamma camera during 20 min followed by sequential static anterior and prone lateral breast images after 30 min and after 2 and 4 h. 57Co-assisted skin marking defined the sentinel node location for subsequent gamma probe, blue dye-guided sentinel node biopsy.

In group A (mean dose, 61.6 MBq; range, 42-88 MBq) scintigraphy revealed lymph nodes in 83 patients (83%), with an increase in the rate of visualization from 72% for 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 for visualization, with optimal results obtained from doses higher than 65 MBq. Lymph nodes were visible in 34 patients (41%) during the first 30 min after injection, whereas in 49 patients appearance occurred at 2-4 h. A total of 97 lymphatic basins were visualized (80 axillary, 3 clavicular, 14 internal mammary). In group B (mean dose, 90.8 MBq; range, 68-124 MBq), the visualization rate was 94%, with early lymph node appearance in 27 patients (57%) and a total of 53 basins (45 axillary, 8 internal mammary). In combination with intraoperative blue dye mapping and y probing, the identification rate increased to 90% in group A and 98% in group B. Prone lateral images contributed to identification of intramammary lymph nodes in a total of 14 patients and axillary nodes close to the injection site in 8 other patients.

Mammary lymphoscintigraphy by single intratumoral injection is a valid method for lymphatic mapping and identification of both axillary and nonaxillary sentinel nodes. Lymph node visualization appears to be improved with higher tracer doses. The compactness of the injection site enables high-quality additional lateral images that can depict intramammary or axillary lymph nodes adjacent to the injection site.