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To the Editor. granulocytes in vivo. However, it has not been detected on ery-CD33 antigen (glycoprotein M, 67,000). detected by the mono-We successfully detected the expressions of CD33 antigen on norclonal antibodies (MoAbs) MY-9 and Leu-M9, is in highest conmal human peripheral CD4+ T and CD8' T lymphocytes that were centration on immature myelocytic cells and on monocytes in mar-activated with anti-CD3 MoAb (OKT-3) plus recombinant inrow and peripheral blood. and it is weakly expressed by mature terleukin-2 (rIL-2). The normal human peripheral CD4+ T and throid cells, platelets, or normal lymphocytes.'.2

Although aberrant T/NK-cell antigen expression is observed approximately 10% of B cell precursor acute lymphoblastic leukemia (BCP-ALL), the bright positivity of CD56 is exceedingly rare [1-3]. Here, we describe the first reported case, at least to our knowledge, of KMT2A-AFF1-rearranged BCP-ALL that co-expressed CD34, CD19, cytoplasmic (cyt) CD79a, and CD56 without any other lineage markers developed in a pregnant woman and successfully treated by allogeneic hematopoietic cell transplantation. A 33-year-old woman in her third trimester was referred to our department because of extreme hyperleukocytosis reaching 300 × 10 9 /L with 96% of leukemic blasts (Fig. 1a). Flow cytometric analysis of bone marrow leukemic cells revealed the bright surface expression of CD34 and CD56 as well as the positivity of CD19, CD38, and HLA-DR with partial expression of cyt CD79a, while CD3, CD10, cyt myeloperoxidase, cyt CD3, cyt CD22, and cyt μ heavy chain were found to be negative (Fig. 1b). CD4 was also negative (data not shown) and there was no morphological findings that suggest monocytic differentiation. Cytogenetic analysis

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