CD 34 or cluster of differentiation 34, is a cell surface antigen expressed on human hematopoietic progenitor cells and also endothelial cells that are proliferating. This is useful for assisting in diagnosis of conditions like AML or acute myeloid leukaemia. CD34 is normally found on endothelial cell also found in hemopoeitic cells like those found in bone marrow or umbilical cord. Because it found on endothelial cells, this makes this a useful tool to identify if a tumour is of vascular origin. This shows a membraneous staining pattern as shown below.

Picture 1 – CD 34 positivity in tonsil

CD 34 has several different applications. Below are a few examples.