LYMPHATIC DIAMETERS AND RADIONUCLIDE CLEARANCE IN A MURINE MELANOMA MODEL

Objectives: To determine the clearance of a radionuclide from various sizes of footpad melanomas via lymphatics and to measure the diameters of these vessels. Design: Nonrandomized animal study. Setting: A hosp ital research laboratory. Subjects: C57BL/6 mice. Interventions: Femal e mice were injected in the right rear footpad with B16 F10 cells that were allowed to grow to either 1, 2, 3, 4, or 5 mm in anteroposterior diameter. Clearance from feet with or without tumors of injected tech netium Tc 99m human serum albumin ((99m)TcHSA) was assessed for 200 mi nutes. Calf lymphatic diameters were measured using aniline blue dye. Results: The clearance of the injected (99m)TcHSA from mouse footpads without tumors was 1.26 +/- 0.18 x 10(-4) mL/min x cm(3) of tissue. Cl earance increased 2.24-fold to 2.82 +/- 0.12 x 10(-4) mL/min x cm(3) o f tissue from l-mm tumors and to 6.20 +/- 0.08, 6.11 +/- 0.13, 6.91 +/ - 0.58, and 7.23 +/- 0.48 x 10(-4) mL/min x cm(3) of tissue from 2-, 3 -, 4-, and 5-mm tumors, respectively (P<.05). Calf lymphatic diameters increased from 75.41 +/- 9.72 mu m in naive, nontumor-bearing mice to 93.51 +/- 7.12, 111.61 +/- 27.07, 126.69 +/- 25.20, 124.43 +/- 24.75, and 127.44 +/- 25.35 mu m in mice bearing 1-, 2-, 3-, 4-, and 5-mm tu mors, respectively (P<.01). Conclusions: There was a size-dependent, d irect correlation between increasing tumor size in the footpad and inc reasing diameter of lymphatics draining the footpad. Clearance of inje cted (99m)TcHSA from these tumors also exhibited a similar positive co rrelation with tumor size.