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Autor*: S. Valníček
Description:
More than 80% of blasts in AML M5a have to be monoblasts to fulfill the criteria for for the diagnosis of acute monoblastic leukaemia M5a. In contrary, in AML M5b promonocytes and monocytes must dominate. Monoblasts are large cells with mostly round nuclei, in most cases containing nucleoli, with moderate basophilic cytoplasm, often with cytoplasmic vacuoles
and usually with azurophilic powdering. Myeloperoxidase is usually negative, or almost negative. Non-speciphic esterase positive, according to Collins in more than 80% of cells, with blockade after adding NaF , BE positive in 80% or more, granular PAS positivity is weak positive with diffuse positive background (Hayhoe).
Zařazení*:
Acute monoblastic and monocytic leukaemia
Přílohy*:
Description: Solitaire blast cell in peripheral blood smear from this patient. Distinct nucleoli and aberrant chromatine are apparent. Morphologic diagnosis ONLY from peripheral blood is not possible in this case see bone marrow). 
Description: Numerous relatively large monoblasts with round, oval, sporadic lightly lobular nuclei. Nucleoli in this case not clearly seen, cytoplasm moderately basophilic with fine powdering of azurophilic granulastion and with distinct vacuoles.
Description: M5a blasts are MPOX negative. Relatively mature normal granulocyte gives however strong MPOX positivity on this picture.
Description: Blasts in this case SB negative, in some of them 1-2 weekly positive granules only. 
Description: Granular positIvity of PAS reaction with only very mild positive background.
Description: Strong positivity of BE in all monoblasts. On the right side of the picture, there is a lymphocyte nearby the blast with dot like
BE-positivity (T-lymphocyte).
Description: Complete Na-fluoride blockade of BE staining in monoblasts. Compare with previous picture withouth NaF.
Description: Strong ANE positivity in monoblasts.