I've a clinical puzzle. 2 year old boy presenting with severe thrombocytopenia, platelets 21x10^9/l, Hb 10.9g/dl, WBC 16x10^9/L. Clinically, the child is well without any organomegaly. The peripheral blood film shows a few blasts with some other atypical, large immature mononuclear cells. An acute Lymphoblastic Leukaemia was the clinical suspicion and a marrow exam was done. This was moderately hypercellular with preserved normal haematopoiesis but scanty megakaryocytes. There were a number of the same atypical MNC appearing singly as well as in groups. The morphologic appearance suggested a neuroblastoma. Cytochemical stains were all negative. The trephine biopsy also suggested a neuroblastoma. There is however no evidence of a extramedullary tumour and catecholamines are not raised. The cells in the peripheral blood were flowed with the following results. 13% of peripheral blood cells were CD45 negative or very dim (dimmer than grans and similar to erythroblasts). They were CD34+/19 dim/33 dim/ 56 dim/ Tdt - / cy MPO - / 61+ / 42a +/ Glycophorin-A -. Fluoresence microscopy confirmed the CD42a & CD61 results. Are these then megakaryoblasts, undifferentiated blasts or neuroblastoma cells? There have been reports from Germany that neuroblastoma cells express the CD34 marker. Any opinions? Te-Chih. Liu, Te-Chih MD Laboratory Haematology National University Hospital Singapore 119074 Tel: (65) 7725353 Fax: (65) 7751757
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