KRAS and histiocytic sarcoma: In this regard, it is intriguing that in our study, we observed variable expression of the lymphoid marker CD8 in a subset of leukemic mice transplanted intravenously with p16p19−/−; Kras(G12V) cells, whereas CD8 was less frequently expressed in histiocytic sarcomas generated by intramuscular transplantation of the same donor cell population.