To test directly the tumor-propagating potential of p16p19−/−; Kras(G12V) histiocytic sarcomas, GFP+ cells from primary tumors induced in the muscles of primary NOD.SCID recipients were sorted using FACS and defined numbers of sorted cells were transplanted into the cardiotoxin pre-injured gastrocnemius muscle of secondary NOD.SCID recipients (Fig. 5A). The gene discussed is KRAS; the disease is neoplasm.