Intradermal radioisotope injection is superior to subdermal injection for the identification of the sentinel node in breast cancer patients.

BACKGROUND AND OBJECTIVES: The purpose of the present study was to evaluate whether the intradermal injection of radiocolloids would improve the identification rate of sentinel nodes over the subdermal injection in breast cancer patients.

METHODS: Sentinel node biopsy was performed in T2 breast cancer patients with clinically negative nodes, using subdermal or intradermal injection of radioisotopes with the peritumoral dye injection. We used Tc-99m tin colloid, with a larger particle size (0.4-5 microm), rather than sulfur colloid and colloidal albumin.

RESULTS: The initial 55 patients underwent subdermal injection of radiocolloids; the next 61 patients underwent intradermal injection of radiocolloids for sentinel node biopsy. The detection rate of sentinel nodes was significantly (P = 0.048) higher in the intradermal injection group (61/61, 100%) than in the subdermal injection group (51/55, 92.7%). False-negative rates were comparable between the two groups. Lymphoscintigraphy visualized the sentinel nodes significantly (P < 0.0001) more often in the intradermal injection group (59/61, 96.7%) than in the subdermal injection group (20/54, 37.0%).

CONCLUSIONS: A significantly higher identification rate of sentinel node biopsy and lymphoscintigraphy can be achieved by intradermal injection of Tc-99m tin colloid with a large particle size than by subdermal injection.