Histopathology of Ptpn11^D61Y-evoked MPD.Ptpn11^D61Y mice show marked increase of mature myeloid elements in the peripheral blood (×400), bone marrow (×400), and spleen (×20 and ×400), as well as myeloid infiltration in the liver (×100). Myeloid infiltration in the white pulp of Ptpn11^D61Y spleen is indicated by arrows (spleen ×20). Whereas control spleens contain mainly immature RBCs (arrows, spleen ×400), mutant spleens show increased myeloid cells (arrowheads, spleen ×400).