CD5: Difference between revisions
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<span style="color:navy">'''Diagnostic role'''</span> | <span style="color:navy">'''Diagnostic role'''</span> | ||
*CD5 is expressed by almost all cases of CLL/SLL and the majority of cases of mantle cell lymphoma (90%) | |||
*However, CD5 can be expressed by marginal zone lymphoma (15%); lymphoplasmacytoid lymphoma (5-10%); and occasionally diffuse large B cell lymphomas (10%) (where it may be associated with poorer prognosis and Activated B Cell (ABC) subtype). | *However, CD5 can be expressed by marginal zone lymphoma (15%); lymphoplasmacytoid lymphoma (5-10%); and occasionally diffuse large B cell lymphomas (10%) (where it may be associated with poorer prognosis and Activated B Cell (ABC) subtype). |
Revision as of 17:19, 30 April 2023
- Summary
- This marker is expressed by normal T cells and a subset of normal B cells, however it main diagnostic role is in diagnosis of certain B cell disorders:
- In mature B cell neoplasms CD5 is used to indicate likely CLL or MCL (both have consistent expression of CD5)
- In acute lymphoblastic leukaemia CD5 is useful to indicate T lineage, with (relatively) low levels of aberrant expression
- It has low frequency of expression on other lymphoma types.
Normal expression and function
CD5 binds to the B-cell ligand CD72, and has a negative effect on T and B cell receptor signalling raising the threshold for response to antigen (possibly limiting responses to self-antigens). It is a pan T cell antigen (present on thymocytes and mature T cells) that is also expressed on a subset of B cells (B1 subset comprising around 10% of adult B cells, but with a wide range according to age and disease state). CD5 is expressed at higher level on T cells than B cells, and expression is increased on activation.
Diagnostic role
- CD5 is expressed by almost all cases of CLL/SLL and the majority of cases of mantle cell lymphoma (90%)
- However, CD5 can be expressed by marginal zone lymphoma (15%); lymphoplasmacytoid lymphoma (5-10%); and occasionally diffuse large B cell lymphomas (10%) (where it may be associated with poorer prognosis and Activated B Cell (ABC) subtype).
- CD5 is expressed by most mature T cell neoplasms (with the exception of hepatosplenic T Cell lymphoma and T cell large granular lymphocytic leukaemia).
- CD5 is useful in the diagnosis and classification of T cell acute lymphoblastic leukaemia (T-ALL) since it is positive in 90% of T-ALL, although expression may be dim or absent in early precursor T ALL.
Other relevant information:
Aberrant expression of CD5 by B-ALL (rare) or AML (around 10%) is described, but in both cases CD5 expression appears less common compared with other “ambiguous markers”.
SUMMARY TABLES