Tumor–immune interactions and cancer cell material within pulmonary lymphatics. (A) Schematic diagram summarizing the B16.F10-ZsGreen melanoma mouse model. (B–E) Images of intralymphatic leukocytes without melanoma material, leukocytes carrying melanoma material, and melanoma cell/cell fragments in lymph flow, with (C) the quantification of total leukocyte flow and (D and E) proportions of cells observed in lymphatics. (F and G) (F) Overview showing metastatic tumor in lung with (G) the quantification of enrichment of bronchovascular cuff space (“cuff”) relative to respiratory (“resp.”) lung. (H) Image showing melanoma cells in a lymphatic vessel adjacent to an accumulation of melanoma material either in or adjacent to a lymphatic. Graphs show means ± SEM. P values are from (C) a Mann–Whitney U-test; and (G) a two-tailed paired t test. Group sizes: (B and D) n = 6, (C) n = 4–6, (F) n = 4.