Promyelocyte

Scheme electron microscopy. The large promyelocyte (15-25 μm) contains a nucleus (1) with one or two nucleoli, the rough endoplasmic reticulum (4) is present and show many expanded profiles. Distinct also are numerous ribosomes and a well-developed Golgi area (2) where 'non-specific', primary or azurophilic granules (3, here with different densities) are formed. These granules contain among others myeloperoxidase, acid phosphatase and arylsulfatase.