A, H&E staining and Ki-67 immunostaining of the lung tissue sections in mice bearing orthotopic MDA-MB-231 tumors (sacrificed on day 28). Metastatic tumor nodules were counted in the five lobes of the lungs and the quantification is shown on the right. B, Images of the mesenteric lymph nodes harvested from mice bearing orthotopic MDA-MB-231 breast tumors. C, H & E staining and Ki-67 immunostaining of the mesenteric lymph node tissue sections in mice bearing orthotopic MDA-MB-231 tumors. Quantification of Ki-67-positive cells was determined microscopically (mean cell number per field ± SD, 12 fields per lymph node) and is shown on the right. D, H & E staining and Ki-67 immunostaining of the lung tissue sections in mice bearing subcutaneous LLC tumors (sacrificed on day 12). Metastatic tumor nodules were counted in the five lobes of the lungs and the quantification is shown on the right. E, Images of mesenteric lymph nodes harvested in mice bearing subcutaneous LLC tumors. F, H & E staining and Ki-67 immunostaining of the mesenteric lymph node tissue sections in mice bearing subcutaneous LLC tumors. Quantification of Ki-67-positive cells was determined microscopically (mean cell number per field ± SD, 12 fields per lymph node) and is shown on the right. The data are reported as the mean ± SD (n = 5). *, p < 0.05. **, p < 0.01.