CD33 (gp67 and p67) is a specific hematopoietic marker, which is expressed in monocytes/macrophages, granulocyte precursors (decreases with maturation), mast cells, and dendritic cells.

 

Diagnostically, CD33 is helpful in differentiating myeloid tumors for lymphoid neoplasms.  Myelomonocytic and monoblastic leukemias may mark with CD33, but are usually negative for myeloperoxidase (MPO).  Hematodermic neoplasm is also negative for CD33.

 

Bone Marrow IHC.  Torlakovic, EE, et. al. American Society for Clinical Pathology Pathology Press © 2009.  pp. 84.