Background: This study was designed to investigate the relationships among primary tumor size, lymphatic vessel diameters, the incidence of sentinel lymph node (SLN) metastasis and lymphatic clearance from murine footpad melanomas.
Methods: Lymphatic clearance (LC) of [99mTc]HSA from the middle of the footpad of syngeneic C57BL/6 mice, with or without primary melanomas (sizes varying from 1 to 5 mm in anteroposterior diameter), was quantitated using a gamma scintillation detection system. Lymphatic vessel diameters (LD) were measured after injection of aniline blue dye into footpad tumors. The incidence of SLN, femoral lymph node (FLN), and lung metastases was recorded.
Results: Metastasis to SLNs increased as tumor growth progressed (r = 0.976, p = 0.001), and there was a correlation between tumor size and both FLN (p = 0.041) and lung (p = 0.055) metastases. There was also a correlation between lymph node metastasis and LC (r = 0.83, p = 0.04) and LD (r = 0.84, p = 0.04).
Conclusions: These studies support the hypothesis that lymph flow and LD is increased in experimental murine melanomas and this relates to both primary tumor size and to lymphatic and hematogenous metastasis.