Dear list members Have you ever seen a case of CD45 (leukocyte common antigen)-negative acute leukemia? The male patient was in his early 30's and visited our hospital with chief complaint of low platelet number. He felt fatigue and experienced easy bruisability but looked well. At the time of visit on Jan 6, 1998, the CBC data was WBC 6,000/uL, Hb 8.5 g/dL, platelet 24K/uL. The peripheral blood smear showed 30% leukemic blasts and bone marrow revealed 89.6% medium sized leukemic blasts with high N/C ratio, fine chromatin, and absent to one nucleolus. Cytochemical stain was done; peroxidase (-), SBB (-), PAS (pinkish background staining), Non-specific esterase (-). Flow cytometric analysis of bone marrow aspirates revealed a predominant population of cells with a lymphoid light scatter. These leukemic blasts has following immunophenotype; CD34 (+; 94%), HLA-DR (+; 96%), nuclear TdT (+; 92%) CD33 (+; 53%), CD13 (+; 88%), CD61 (-) CD7 (-), CD5 (-), CD2 (-) CD20 (+; 27%), CD1 9 (+; 90%), kappa (-), lambda (-), CD10 (+; 90%) and, interestingly CD45 was negative. We could find CD45-bright normal lymphocytes on CD45-RALS (right angle light scattle) dot plot thus false-negative for CD45 of these leukemic cells was ruled out. Anti-CD45 monoclonal antibody (Beckton-Dickinson Immunocytometry Systems, Cat No. 347463, USA) clone 2D1 conjugated with FITC (IgG1) was used at that time and we confirmed this CD45 negativity with immunostain on bone marrow aspirate smears using DAKO monoclonal antibody. Molecular and cytogenetic studies were also performed and demonstrated minor bcr/abl (e1a2) rearrangement and t(9;22), respectively. We concluded this case as a CD45-negative acute biphenotypic (myeloid and B lymphoid)leukemia. I tried to find out previously reported cases of CD45-negative acute leukemia but failed except some lymphomas. My questions are; 1. Is this case the first one of CD45-negative acute leukemia? 2. If it is not, could any one kindly tell me his/her experience or the source of literature of reported cases? 3. If it is the first one, I want to establish a new cell line with this case. Could you give me a good reference or tips in doing this work? Any comment will be greatly appreciated. Thanks in advance. ================================== Chang-Seok Ki, MD 3rd-year Resident Dept. of Clinical Pathology Samsung Medical Center E-mail. kcdol@samsung.co.kr Tel. 82-2-3410-2707 Fax. 82-2-3410-2719 ==================================
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