Cluster of Differentiation 5 （CD5） is expressed in high levels on the surface of T-cells, while the expression levels and role of CD5 in B-cells is not well documented. As a part of a diagnostic panel, its utility lies predominantly as a marker for T-cells, with over 70％ of T-cell neoplasms expressing CD5. In particular, it is correlated with chronic lymphocytic leukemia and small lymphocytic lymphomas, mantle cell lymphoma, as well as a subset of diffuse large B-cell lymphomas. CD5 demonstrates positive expression in thymic carcinomas, and is not as sensitive as CD3. CD5 also has value as a prognostic indicator, as it is associated with poor prognosis in acute T-cell lymphoblastic leukemia.
