Morphologic and Immunophenotypic Features of Hairy Cell Leukemia Involving Lymph Nodes and Extranodal Tissues.

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Morphologic and Immunophenotypic Features of Hairy Cell Leukemia Involving Lymph Nodes and Extranodal Tissues.

Histopathology. 2017 Mar 06;:

Authors: Cortazar JM, DeAngelo DJ, Pinkus GS, Morgan EA

Abstract
Hairy cell leukemia (HCL) is a rare B-cell neoplasm that mainly affects bone marrow (BM), peripheral blood (PB), and spleen. Involvement of lymph nodes and extranodal structures is considered infrequent. Herein we describe our institutional experience of nodal (n=10) and extranodal (n=3) HCL over a thirty-year period. Ten patients had prior evidence of HCL within the BM or PB at a median 35.8 months before nodal/extranodal diagnosis (range, <1 to 175 months), and HCL was diagnosed concurrently within the bone marrow of 1 additional patient. Nodal involvement showed distinct architectural patterns including diffuse (62% of cases), sinusoidal (25%) and nodular (13%). Extranodal involvement was characterized as diffuse infiltration through underlying structures in all cases. Morphologic features ranged from classic "fried-egg" cytology to a plasmacytoid appearance. Nodal/extranodal disease showed an overlapping immunophenotypic profile with other small B-cell lymphomas, including expression of cyclin D1 (70%), CD43 (55%), CD10 (38%) and CD5 (8%). Rates of both CD43 and CD10 reactivity were higher than previously described in leukemic HCL, suggesting expression may be enriched in cases with extramedullary extension. Although uncommon, HCL should be considered in the differential diagnosis of small B-cell neoplasms involving nodal/extranodal sites given the therapeutic implications. In particular, recent discoveries including detection of the BRAF(V)(600E) mutation in nearly all cases of HCL and the availability of an antibody to CD103 for use in paraffin-embedded tissues will facilitate distinction of HCL from other small B-cell lymphomas in the nodal/extranodal setting. This article is protected by copyright. All rights reserved.

PMID: 28261866 [PubMed - as supplied by publisher]

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