[1439] 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.

IHC results in HCL, SMZL, and ENMZL
HCL96/96 (100%)90/97 (92.7%)97/101 (96%)95/99 (96%)97/101 (96%)
SMZL13/13 (100%)9/13 (69%)6/13 (46%)0/13 (0%)1/13 (7.7%)
ENMZL8/10 (80%)7/10 (70%)1/10 (10%)0/10 (0%)0/10 (0%)

In the controls, Annexin-1 stained background normal granulocytes and myeloid precursors and was positive in all myeloid malignancies, T-Lymphoblastic Leukemia (3/3), metastatic adenocarcinoma (1/3), and metastatic melanoma (1/1). T-bet was positive in T-cell Large Granular Lymphocytic Leukemia (3/3), Hodgkin Lymphoma (2/3), Large B-cell Lymphoma (1/3), Peripheral T-cell Lymphoma (3/3) and metastatic adenocarcinoma (3/3).
Conclusions: TRAP, T-bet, DBA.44, Annexin-1, and Cyclin-D1 all stained >90% of HCL cases with TRAP staining 100% of HCLs. Annexin-1 was the only antibody that did not stain any of the SMZL or ENMZL. However, Annexin-1 is limited by its staining of granulocytic precursors and thus is difficult to interpret when the HCL infiltrate is small and intermixed with granulocytes. Cyclin-D1 showed similar sensitivity to Annexin-1 and aberrantly stained only 1 case of MZL; its reactivity in mantle cell lymphoma must also be an interpretation factor. Thus, our results show that a combination of TRAP, Annexin-1, and Cyclin-D1 IHC stains can provide high specificity and sensitivity when HCL is a diagnostic consideration in the evaluation of a low-grade B-cell neoplasm.
Category: Hematopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 191, Monday Morning


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