Tumor-bearing cervical lymph nodes in oral melanoma-bearing mice. (A) The lymph node (LN) metastasis rates of this model at different time points. (B), (C) Photographs showing enlargement and deposition of melanin in cervical LNs 4 (B) and 10 (C) days after injection of B16/F10 melanoma cells into the left side of tongue. After 10 days, tumor-involvement with LNs on both sides is increased (C). (D) Histological grading of melanoma cell invasion in LNs, on hematoxylin and eosin-stained sections, as follows: Grade 1, proliferation of melanoma cells is confined from the marginal sinus to the follicles; Grade 2, invasion of melanoma cells extends within the LN parenchyma; Grade 3, tumor cells occupy >60% of the LN area. Scale bar = 5 μm. (E) Change in LN weight of tumor-bearing sentinel LNs. Weights of tumor-bearing LNs increased significantly, compared with hat controls. Columns, mean; bar, standard error. *, P<0.05 relative to controls.