THE VALUE OF IMMUNOHISTOCHEMISTRY
IN THE ASSESSMENT OF BONE MARROW DISORDERS

Attilio Orazi, M.D., FRCPath. and Dennis P. O'Malley, M.D.

TARTRATE RESISTANT ACID PHOSPHATASE A monoclonal antibody which is capable of demonstrating acid phosphatase isoenzyme 5 (tartrate resistant acid phosphatase) in conventionally fixed tissue sections can be used to identify hairy cell leukemia cells in bone marrow biopsies. Unfortunately, the antibody stains only half of the neoplastic cells in each given HCL case and shows variable reactivity with marginal zone lymphoma, histiocytes, and mast cells. The concomitant expression of DAB.44 and TRAP appears to be limited to HCL cases. References Hoyer et al: Immunohistochemical demonstration of acid phosphatase isoenzyme 5 (tartrate-resistant) in paraffin sections of hairy cell leukemia and other hematologic disorders. Am J Clin Pathol. 1997;108:308-15. Janckila et al: Hairy cell identification by immunohistochemistry of tartrate-resistant acid phosphatase. Blood. 1995 May 15;85(10):2839-44.