CD23 is a cell surface glycoprotein (also known as the low-affinity IgE receptor, FcεRII) expressed on certain types of B lymphocytes and other immune cells.

Immunohistochemistry (IHC) for CD23 is a laboratory test performed on tissue samples to detect the presence and distribution of CD23 protein within cells. The test uses specific antibodies that bind to CD23, allowing pathologists to visualize its expression under a microscope.