CD33 or SIGLEC-3 (sialic acid-binding immunoglobulin-type lectin) is a transmembrane receptor that is expressed ubiquitously in myeloid progenitors, while it is usually found on leukemic myeloid cells (≥80% of AML blasts), and on monocytes, granulocytes, and mast cells, sparing multipotent progenitors and stem cells. This evidence concerns the gene CD33 and acute myeloid leukemia.