[Sudan black B-positive acute lymphoblastic leukemia]

Inasmuch as Sudan black B stain is highly specific for myeloid cells and since over 3% positive blast cells meet the needs of diagnosis for myeloblastic leukaemias, we had the opportunity to study a 27 year-old male with acute leukaemia whose morphological, cytochemical, immunocytochemical (HLA-DR, CD-10, CD-19, CD-20, CD-21 all positive) and ultrastructural features were clearly in accordance with acute lymphoblastic leukaemia, except for 42% Sudan black B positivity of the bone marrow blast cells. The practical interest of this case comes from the necessity to take this rare ALL case into account.