Optimized mammary lymphoscintigraphy using larger colloid particles.

TO THE EDITOR: In their very interesting article on mammary lymphoscintigraphy, Valdés Olmos et al. (1) report on applying a single intratumoral injection for sentinel lymph node (SLN) identification. Only patients with an operable, palpable breast tumor were included in the study. The authors used 99mTclabeled nanocolloid with a particle size of ,80 nm. During the first 30 min, two to eight nodes were visualized in 61% of the patients. In our department we have recently begun using 99mTc-labeled human serum albumin colloid (Senti-Scint; MEDI-Radiopharma, Budapest, Hungary) with a particle size of 100–600 nm in a small volume of 0.5 mL and inject it subcutaneously above the tumor. The visualization rate of the SLN in 35 patients has been 94%, whereas in just three cases (,10%) we observed more than one node in the first 60 min. We believe that this difference in visualization rate is not the result of the difference in injection sites. In accordance with De Cicco et al. (2) and Paganelli et al. (3), we suggest that larger particle size (which is often taken up by only one node) may be more suitable for SLN identification, which can be easily identified by the g-ray–detecting probe during surgery, whereas the use of small particle size increases the risk of sampling non-SLNs during biopsy.