Phenotype of leukemic, hCG–PML-RARα transgenic mice. (A) Spleens from a nontransgenic littermate (left) and an hCG–PML-RARα transgenic mouse (no. 135-448) with leukemia (right). (B) Bone marrow cells from a leukemic mouse (no. 137-1106) stained with modified Wright's Giemsa. This marrow from the leukemic mouse consists predominantly of very immature myeloid cells that contain abundant azurophil granules (black arrowheads). (C and D) Spleen sections from a nontransgenic mouse (C) or a transgenic mouse (no. 135-448) (D) with leukemia, stained with hematoxylin and eosin. Note the effacement of follicular structures by the leukemic infiltrate. (E and F ) Liver sections from a nontransgenic mouse (E) or mouse no. 135-448 (F ) stained with hematoxylin and eosin. Note the infiltration of the liver with immature myeloid cells (white arrowheads).