CD20 is a crucial marker used in the diagnosis and therapeutic targeting of B-cell malignancies, including certain forms of lymphoma and leukemia. The CD20 protein serves as a specific marker for differentiating B-cell stages in both healthy and diseased states.

CD20 is a non-glycosylated phosphoprotein located on the cell membrane. It is involved in the regulation of B-cell activation and proliferation. CD20 is expressed on pre-B cells and mature B cells but is lost as B cells differentiate into plasma cells. This pattern is key to distinguishing stages of B-cell development and identifying cells that are part of the B-cell lineage.

CD20 is an essential biomarker for the diagnosis and treatment of B-cell lymphomas and plays a pivotal role in the management of these diseases. Its role in immunohistochemistry is particularly critical for accurately identifying and characterizing B-cell populations in various hematological conditions.