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Myeloperoxidase Immunoreactivity in Adult Acute Lymphoblastic Leukemia

Daniel A. Arber MD, David S. Snyder MD, Miriam Fine MS, Andrew Dagis MS, Joyce Niland PhD, Marilyn L. Slovak PhD
DOI: http://dx.doi.org/10.1309/HDUE-DN2E-B72E-JK99 25-33 First published online: 1 July 2001


To evaluate the frequency and significance of myeloperoxidase positivity in adult acute lymphoblastic leukemia (ALL), bone marrow biopsy material from 82 adults with ALL was evaluated with a polyclonal myeloperoxidase (pMPO) antibody. Nineteen cases (23%) demonstrated evidence of pMPO immunoreactivity. Positive cases were precursor B-cell lineage, and CD13 or CD15 expression was more frequent than in the pMPO-negative cases. A subset of pMPO-positive cases studied with a monoclonal MPO antibody was negative. Western blot analysis using the pMPO antibody showed the expected 55-kd band for myeloperoxidase in pMPO-positive and pMPO-negative ALLs, suggesting a lack of specificity of this antibody in ALL. Forty-two percent (8/19) of the pMPO-positive ALL cases demonstrated evidence of t(9;22) by either karyotype or polymerase chain reaction analysis. The pMPO-positive ALLs had a lower frequency of extramedullary disease than the pMPO-negative group and a trend toward improved overall survival compared with the pMPO-negative group. Immunoreactivity with pMPO in adult ALL may lead to an incorrect interpretation of biphenotypic acute leukemia using a recently described scoring system, and a revision to that scoring system is proposed to accommodate pMPO-positive ALL.

Key Words:
  • Acute lymphoblastic leukemia
  • Myeloperoxidase
  • Biphenotypic acute leukemia