Apc-heterozygous mice displayed an alteration in the distribution of CD41⁺ megakaryocytes and monocytes. Flow cytometric analysis of mature myeloid cells from BM and spleen (SP) from Mx1-Cre⁺Apc^fl/+ mice and the control Mx1-Cre⁻Apc^fl/+ mice was performed 3 to 4 months after induction. The percentage of (A) Gr-1⁺Mac-1⁺ and Gr^lowMac-1⁺ or (B) CD41⁺cells is indicated (average ± SD of 4 animals). *P < .05; **P < .01.