OBJECTIVETo explore the effects of different injection techniques of radiotracer on the visualization rate of internal mammary sentinel lymph nodes (IMSLN) in breast cancer patients.

METHODSA series of 137 consecutive breast cancer patients was included in this prospective study. Fifty-eight patients (group A) received the radiotracer (99)Tc(m)-sulphur colloid injected only into 1-2 points in the breast parenchyma in one quadrant, and seventy-nine patients (group B) received the radiotracer injection into the breast parenchyma in two quadrants of the breast. The differences of IMSLN visualization rates of the two groups were compared and the relevant affecting factors were analyzed.

RESULTSThe IMSLN visualization rate of the group B (70.9%, 56/79) was significantly higher than that of the group A (13.8%, 8/58) (P < 0.001). Both techniques seemed to be reliable to identify sentinel lymph node in the axilla (98.7% vs. 98.3%, P = 0.825). In addition, the visualization rate of internal mammary hotspots (82.2%) was more commonly seen in patients receiving injection of a larger volume of radiotracer ( ≥ 0.5 ml/point) than those receiving a smaller volume of radiotracer (<0.5 ml/point, 55.9%, P = 0.011).

CONCLUSIONSThe modified injection technique (two quadrants, large volume radiotraver, and ultrasound guidance) can significantly improve the visualization rate of IMSLN. Our findings should make the biopsy of IMSLN widely implemented and provide an effective and minimally invasive technique to evaluate the internal mammary lymph node status.