Annexin-1 and T-bet are recently described immunohistochemical stains that reportedly assist in the diagnosis of hairy cell leukemia (HCL). Our objective was to assess the sensitivity and specificity of a panel of immunohistochemical stains in distinguishing HCL from other B-cell neoplasms, particularly splenic and extranodal marginal zone lymphomas (SMZL and ENMZL, respectively). The study included 234 bone marrow biopsy specimens: 101 HCL, 13 SMZL, and 10 ENMZL cases were assessed with CD20, tartrate-resistant acid phosphatase (TRAP), DBA.44, a-1, T-bet, and cyclin D1, and 110 control cases were assessed with annexin-1 and T-bet. Our study showed that annexin-1 is a specific and sensitive marker for HCL; however, interpretation is limited by positivity within myeloid precursors. T-bet, DBA.44, and TRAP immunohistochemical stains lack sufficient sensitivity and specificity to differentiate HCL from either form of marginal zone lymphoma. However, our data suggest that the addition cyclin D1 to the immunostaining panel will increase the sensitivity and specificity of HCL diagnosis.
"Acknowledging that variations in immunophenotype and immunohistochemical staining patterns often occur in HCL  , the features of the patient described herein, taken together with the molecular characterisation, lead us to conclude that this case represents BRAF V600E-negative HCL. Sequencing and the more sensitive allele-specific PCR approaches failed to detect the mutation while demonstration of the lack of phospho-ERK response to inhibitor, a valid surrogate of the BRAF V600E  , corroborates the lack of RAF/MEK/ERK pathway activation. "
[Show abstract][Hide abstract] ABSTRACT: Since the initial report of the BRAF V600E mutation in hairy cell leukemia, numerous investigators have demonstrated the presence of this activating mutation in nearly all cases of this disease. A case of hairy cell leukemia is documented with a classical clinical, morphological, immunophenotypic, and cytochemical profile in which the BRAF V600E was not detected. The diagnostic and therapeutic implications are discussed.
[Show abstract][Hide abstract] ABSTRACT: This chapter provides an overview of immunohistochemical markers used frequently in assessing bone marrow diseases. These
disease entities include lymphoid and myeloid leukemias, both acute and chronic, lymphoproliferative disorders, T and B cell
neoplasms/lymphomas, myeloproliferative neoplasms, myelodysplastic syndromes, mast cell disease, plasma cell dyscrasias, and
metastatic tumors to the bone marrow.There is quite a bit of overlap between the markers used in the bone marrow workup for
lymphoid diseases and lymphoma (Chap. 27), thus a review of that chapter might be helpful in the workup of lymphoproliferative
disorders. Also the marrow can be the site for metastatic tumors. The workup of metastatic disease to the marrow is the same
as in any other site (Chap. 7) with the exception of markers that are rendered useless by the decalcification process.
KeywordsBone marrow-T and B cells-Blast-Acute lymphoblastic leukemia-Acute myelogenous leukemia-Myeloproliferative neoplasms-Myelodysplastic syndromes-Lymphoma-Chronic
Handbook of Practical Immunohistochemistry, 06/2011: pages 493-500;
[Show abstract][Hide abstract] ABSTRACT: Recently, the BRAF V600E mutation was reported in all cases of hairy cell leukemia (HCL) but not in other peripheral B-cell neoplasms. We wished to confirm these results and assess BRAF status in well-characterized cases of HCL associated with poor prognosis, including the immunophenotypically defined HCL variant (HCLv) and HCL expressing the IGHV4-34 immunoglobulin rearrangement. Fifty-three classic HCL (HCLc) and 16 HCLv cases were analyzed for BRAF, including 5 HCLc and 8 HCLv expressing IGHV4-34. BRAF was mutated in 42 (79%) HCLc, but wild-type in 11 (21%) HCLc and 16 (100%) HCLv. All 13 IGHV4-34(+) HCLs were wild-type. IGHV gene usage in the 11 HCLc BRAF wild-type cases included 5 IGHV4-34, 5 other, and 1 unknown. Our results suggest that HCLv and IGHV4-34(+) HCLs have a different pathogenesis than HCLc and that a significant minority of other HCLc are also wild-type for BRAF V600.
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