Report of a case of Biphenotypic Acute Leukemia according to EGIL criteria

Acute leukemia demonstrating immunophenotypic features of more than 1 cell lineage are referred to as acute leukemia of ambiguous lineage in the World Health Organization classification system. A subtype of acute leukemia is biphenotypic acute leukemia in which the malignant cell population expresses markers of 2 different lineages. This entity has been defined by a scoring system proposed by the European Group for the Immunological Characterization of acute leukemias (EGIL). Cases having a score of greater than 2 for the myeloid and either the B- or T-lymphoid lineages are regarded as biphenotypic acute leukemia in this system. We report morphological, cytochemical, immunophenotypical, and cytogenetic features of a case of acute leukemia referred to our flow cytometry center of Iranian Blood Transfusion Organization (IBTO) in Tehran-Iran. Peripheral blood and bone marrow samples of a 52 year-old man with previous diagnosis of AML was submitted to flow cytometry department of IBTO for final diagnosis. Morphology, cytochemistry, and immunophenotypic features of blast cells were studied. Blast cells stained with Wright, were relatively large, with high N/C ratio, and often without any granules. Cytochemical stains (MPO, SBB, NSE, PAS) were negative. Multicolor flow cytometric analysis showed that BM blasts expressed CD19, CD20, CD7, and TdT as lymphoid markers, CD13, CD15, and CD117 as myeloid markers, D34 and HLA-DR as stem cell markers. Cytogenic analysis revealed a normal karyotype. Considering the morphology and CD13 positivity, the patient was diagnosed as a case of MO-AML. The patient was treated with AML chemotherapy regimen. He died 5 months later due to the relapse of the disease. BAL is a rare case of acute leukemia with poor prognosis that can not be diagnosed with morphology and cytochemical stains. Although its clinical and biological significance is not yet determined but correct diagnosis and classification of this disease according to accepted and standard criteria like those of EGIL may help to achieve this aim, improve prognosis, and select a specific therapy.