The Role of Immunohistochemistry (IHC) in the Diagnosis of Hairy Cell Leukemia (HCL)
MJ Sherman, CA Hanson, JD Hoyer. Mayo Clinic, Rochester, MN
Background: The diagnosis of HCL is based on a combination of morphologic, cytochemical, and immunophenotypic findings. Paraffin section IHC is often used when evaluating HCL and complements other diagnostic tools. The sensitivity and specificity of IHC for HCL has not been addressed in a large review, particularly for newer markers, such as Annexin-1 and T-bet. We also wished to determine what combination of IHC stains is most effective in differentiating HCL from other low-grade B-cell neoplasms, in particular splenic marginal zone lymphoma (SMZL).
Design: 234 bone marrow biopsies from the Mayo Clinic files (101 HCL, 13 SMZL, 10 extranodal marginal zone lymphoma (ENMZL), and 110 control cases composed of neoplastic and non-neoplastic hematologic conditions and metastatic malignancies) were reviewed. All SMZL and ENMZL cases were confirmed by tissue diagnosis. Assessment of CD-20, TRAP, DBA.44, T-bet, Annexin-1, and Cyclin-D1 stains was performed on the HCL, SMZL, and ENMZL cases. Control cases were assessed with T-bet and Annexin-1.
|HCL||96/96 (100%)||90/97 (92.7%)||97/101 (96%)||95/99 (96%)||97/101 (96%)|
|SMZL||13/13 (100%)||9/13 (69%)||6/13 (46%)||0/13 (0%)||1/13 (7.7%)|
|ENMZL||8/10 (80%)||7/10 (70%)||1/10 (10%)||0/10 (0%)||0/10 (0%)|