MEC1 cells injected subcutaneously localize in several organs of Rag2^−/−γ_c^−/− mice. Organs from Rag2^−/−γ_c^−/− male mice injected subcutaneously with MEC1 cells expressing GFP and killed when the tumor volume reached a dimension of 1000 mm³ were collected and analyzed by confocal microscopy (spleen, kidney, liver, axillary tumor-draining lymph node, bone marrow, and tumor represented in panels A, B, C, D, E, and F, respectively). The extent and pattern of invasion is demonstrated by the presence of green GFP⁺ leukemic cells. Cell nuclei were stained with TO-PRO3 showing in red.