Background and objective: Dermal and intraparenchymal (IP) injections of radiocolloid have been used for lymphoscintigraphic identification of the sentinel node (SN) in breast cancer. Because of our institute's extensive experience with dermal and IP lymphoscintigraphy for melanoma and breast cancer, we compared patterns of lymphatic migration after both types of injections to identify any differences in drainage patterns or SN identification.
Methods: Lymphoscintigrams (n = 31) after dermal injections in 30 patients with primary cutaneous melanoma on the breast were compared with lymphoscintigrams after IP injections in 97 consecutive patients with breast cancer. In each case, 400 microCi of filtered 99mTc-sulfur colloid was injected in four quadrants around the tumor or in the biopsy cavity. All lymphoscintigrams were reviewed for patterns of migration and SN location.
Results: Five of 31 (16%) dermal injections demonstrated bilateral axillary migration (n = 3) or a suprasternal SN (n = 2), neither of which was found with IP injections. Conversely, 3 of 97 (3%) IP injections demonstrated direct supraclavicular (n = 2) or costal margin (n = 1) nodes (P = .006), neither of which was found with dermal injections. Low axillary SNs were noted after 26 (84%) dermal and 93 (96%) IP injections (P = .037). The incidence of extra-axillary SNs was 26% (8 of 31) in the dermal group but only 5% (5 of 97) in the IP group (P = .0027).
Conclusion: There is a significant difference in lymphatic drainage and SN localization between dermal and IP lymphoscintigraphy. This finding has implications for injection techniques when lymphatic mapping of the SN is undertaken to stage a breast carcinoma.