CD21

CD21 is the C3d complement receptor. Antibodies are effective on paraffin-embedded tissue1.

Immunohistochemical expression

• Follicular dendritic cells (FDC)

• B lymphocytes ( in cryostat sections only)

CD35 shows similar staining of FDCs.

Diagnostic utility

Demonstration of the follicular dendritic cell meshwork of follicles in:

• HIV lymphadenopathy in which the follicles may be large and geographical, occupying much of the lymph node (progressive generalised lymphadenopathy stage I) or atrophic (PGL stage II)

• Follicle centre cell lymphomas show tight well developed meshworks, in contrast to the loose networks seen in mantle cell lymphoma.

• Interspersed FDC in mantle cell lymphoma / multiple lymphomatous polyposis of the colon

• The nodules of nodular lymphocyte predominant Hodgkin's disease show a similar meshwork, but its outline is often more complex than that of the follicles of FCC lymphoma and may even be cerebreform.

• Residual germinal centres colonised by low-grade MALT lymphomas

• T cell lymphoma of angioimmunoblastic type, in which the FDC meshwork is around hyperplastic venules. Most peripheral T-cell lymphomas lack FDC networks.

• Castleman's disease (angiofollicular hyperplasia)

• FDC tumours

• Differentiation of Quilty lesions from acute cellular rejection after cardiac transplantation. Quilty lesions consist of an aggregate of CD20+ B-cells, with a rim of CD3+ T-cells. Most Quilty lesions, particularly those over 0.3 mm in size, have a network of CD21+ follicular dendritic cells. Foci of acute cellular rejection lack this structures and are usually devoid of CD21+ follicular dendritic cells2.

References

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

2 Sattar HA, Husain AN, Kim AY, et al. The presence of a CD21+ follicular dendritic cell network distinguishes invasive Quilty lesions from cardiac acute cellular rejection. Am J Surg Pathol 2006; 30:1008-13

This page last revised 19.9.2006.

©SMUHT/PW Bishop