CD20

CD20 is a 35 kDa transmembrane protein involved in B-cell activation. It is expressed early in B-cell ontogeny with loss of expression in terminal B-cell differentation2.

All available antibodies are reactive in paraffin-embedded tissue1.

Immunohistochemical expression

• All mature B lymphocytes but not plasma cells

• Most B cell lymphomas

• About 50% of B cell lymphoblastic lymphomas are CD20 positive

• Some T lymphocytes show weak staining.

• Rare T-cell lymphomas2,3

• some myelomas

It is usually negative in:

• B-precursor lymphoblastic lymphoma

• plasma cell disorders including plasma cell myeloma

Diagnostic utility

• B cell lymphomas

  • Diffuse large B-cell lymphoma with plasmacytoid features is likely to be positive for CD20, CD45 and cytoplasmic IgM, while anaplastic plasmacytoma is likely to be negative for CD30, CD45 and cytoplasmic IgG/A.

  • Positivity of B-cell lymphoma for CD20 may be a criterion for therapy with the humanized monoclonal anti-CD20 antibody, rituximab.

• Hairy cell leukaemia

See: comparison of sensitivities and specificities of T and B cell markers

References

1 Leong A S-Y, Cooper K and Leong FJ W-M. Manual of diagnostic antibodies for immunohistology. 2nd edition, 2003

2 Quintanilla-Martinez L, Preffer F, Rubin D, et al. CD20+ T-cell lymphoma. Neoplastic transformation of a normal T-cell subset. Am J Clin Pathol 1994; 102:483-9

3 Yokose N, Ogata K, Sugisaki Y, et al. CD20-positive T cell leukemia/lymphoma: case report and review of the literature. Ann Hematol 2001; 80:372-5

©SMUHT/PW Bishop