CD22, BL-CAM

CD22 is a 135 kDa transmembrane glycoprotein with expression restricted to B-cells. REcombinant immunotoxic Anti-CD22 has been used in the treatment of hairy cell leukaemia2.

Immunohistochemical expression

Cytoplasmic expression occurs in immature B cells with membrane expresion on mature B cells.

• It is strongly expressed by hairy cell leukaemia and its variants

• weakly expressed by CLL.

• some B-ALL/B-LBL: cytoplasmic staining is considered lineage-specific

Diagnostic utility

• The differentiation of diffuse large B-cell lymphoma and nodular lymphocyte predominance Hodgkin lymphoma (both positive) from classical Hodgkin lymphoma (negative)1 .

References

1 Browne P, Petrosyan K, Hernandez A, et al. The B-cell transcription factors BSAP, Oct-2, and BOB.1 and the pan-B-cell markers CD20, CD22, and CD79a are useful in the differential diagnosis of classic Hodgkin lymphoma. Am J Clin Pathol 2003; 120:767-77

2 Kreitman RJ, Squires DR, Stetler-Stevenson M, et al. Phase I trial of recombinant immunotoxin RFB4(dsFv)-PE38 (BL22) in patients with B-cell malignancies. J Clin Oncol 2005; 23:6719-29

©SMUHT/PW Bishop