Identification of sentinel lymph nodes by contrast‐enhanced ultrasonography with Sonazoid in patients with breast cancer: a feasibility study in three hospitals

The aim of this prospective study was to evaluate the feasibility of periareolar injection of the contrast agent Sonazoid ( SNZ ) followed by ultrasonography ( US ) for the identification of sentinel lymph node ( SLN ) in breast cancer patients with clinically negative node. Patients ( n  = 100) with T1‐2N0M0 breast cancer received a periareolar injection of SNZ followed by US to identify contrast‐enhanced SLN . Each contrast‐enhanced SLN underwent fine needle aspiration cytology ( FNAC ) followed by SLN biopsy with a conventional method using blue dye and/or radiocolloid (B/R). In almost all cases, contrast‐enhanced lymphatic vessels were clearly visualized by US soon after the periareolar injection of SNZ and the SLN s were easily identified with an identification rate of 98% (98/100) for SNZ and 100% (100/100) for B/R. The number of SLN s identified by SNZ ( SNZ ‐ SLN ) (mean per patient, 1.52) was significantly lower than that identified by B/R (B/R‐ SLN ) (2.19) ( P  < 0.0001). Twenty‐five patients with positive SLN s had at least one positive SNZ ‐ SLN . On a node‐by‐node basis, sensitivity, specificity, and accuracy of FNAC for SNZ ‐ SLN s ( n  = 149) were 33.3%, 99.2%, and 85.9%, respectively. Identification of SLN by periareolar injection of SNZ is a technically simple method with an identification rate as high as 98%. SNZ ‐ SLN thus seems to be a good target for FNAC , but sensitivity of FNAC for SNZ ‐ SLN s needs to be improved.