Hairy cell identification by immunohistochemistry of tartrate-resistant
acid phosphatase
AJ Janckila, EM Cardwell, LT Yam and CY Li
Medicine Service, Veterans Affairs Medical Center, Louisville, KY 40206,
USA.
Tartrate-resistant acid phosphatase (TRAcP) has been an indispensible
marker for hairy cell leukemia (HCL) for over two decades. However, the
traditional TRAcP cytochemical stain cannot be performed effectively on
sections of paraffin-embedded tissues that are important resources for
histopathologic evaluation in diagnosis and treatment of HCL. Wide
variation in expression of TRAcP activity by hairy cells (HCs) within and
among patients is an interesting biologic phenomenon that has not been
explained and can cause some diagnostic uncertainty as well. To solve the
problem of staining TRAcP in paraffin sections and to begin to address the
questions of variable TRAcP expression in HCL, we developed a monoclonal
antibody to TRAcP, 9C5, for immunohistochemical identification of HCs. In
smears of blood and bone marrow, immunocytochemistry of TRAcP using 9C5 was
as specific but slightly less sensitive than direct cytochemical staining
of enzymatic activity. In paraffin sections of spleen and bone marrow from
HCL patients, immunohistochemistry with 9C5 stained the HCs with high
sensitivity and specificity and clearly showed the characteristic diffuse
infiltration by HCs. Other cells noted to stain strongly with 9C5 were
occasional macrophages in bone marrow smears and osteoclasts and occasional
tissue macrophages in paraffin sections. These are cells known to express
abundant TRAcP activity. Immunohistochemistry with anti-TRAcP monoclonal
antibody 9C5 may have utility as an added option in the diagnosis of HCL,
as a means to evaluate residual disease in HCL patients undergoing new
treatments, and as a way to address questions regarding variable expression
of TRAcP activity by HCs within and among patients with HCL. Also, 9C5 has
potential as a reagent for the immunoassay of bone-derived serum TRAcP in
patients with certain bone diseases and cancers with bone metastasis.
Volume 85,
Issue 10,
pp. 2839-2844,
05/15/1995
Copyright © 1995 by The American Society of Hematology
