The Pathology Dictionary Team
March 3, 2023
CD45, also known as leukocyte common antigen (LCA), is a protein that is expressed on the surface of all hematopoietic cells and their progenitors, with the exception of erythrocytes (red blood cells) and platelets. Hematopoietic cells include cells of the immune system, such as B cells, T cells, natural killer (NK) cells, monocytes, and granulocytes.
CD45 is a type of protein called a tyrosine phosphatase. It plays a critical role in regulating cell signaling pathways that are important for immune cell activation and differentiation.
In pathology, CD45 is used as a marker of hematopoietic cells and it helps to identify hematopoietic cells such as T cells and B cells in tissue samples. Common tests performed to look for CD45 in a tissue sample include immunohistochemistry and flow cytometry.
Positive for CD45 means that the cells in the tissue sample make CD45.
Negative for CD45 means that the cells in the tissue sample do not make CD45.
Most types of lymphomas (cancers made up of immune cells) are positive for CD45. In contrast, other types of cancer including carcinomas and sarcomas are typically negative for CD45.