We therefore introduced oncogenic Kras into p16p19−/− bone marrow cells by ex vivo gene transduction, and then transplanted these genetically altered cells to induce systemic leukemias (by retro-orbital injection), as well as to produce the first transplantable model of murine histiocytic sarcoma (by injection into the gastrocnemius muscles of NOD.SCID mice). Here, KRAS is linked to histiocytic sarcoma.