Granulocytes have two types of granules primary and secondary. Primary granules are azurophilic, most numerous and prominent at the promyelocyte stage (see morphology of myeloid precursors) and diminish in number with further maturation. As the granulocyte matures the staining characters of the primary granules changes. They initially become violet and then became inapparent because they fail to take up stain. The secondary granules appear in the myelocytes and persist for the rest of the ice of the granulocyte. Neutrophils have fine pink secondary granules.
In conditions of intense stimulation of neutrophil maturation the primay granules may continue to take up stain in mature neutrophil because of a higher concentration of acid mucosubstances. These are called as toxic granules and the change called toxic change. The toxic granules are so called because they were first described in patients with gram negative sepsis and endotoxemia but may be found under conditions of intense stimulation of neutrophil production. The may be seen in
- Inflammatory diseases
- Use of haemopoietic growth factors (G-CSF or GM-CSF)
Described by Pappenheimer in 1945, the Pappenheimer bodies are basophilic erythrocytic inclusions that are usually located at the periphery of the cell. They contain iron and stain with Prussian blue. They also stain with Romanowsky stains because of co-precipitation of ribosomes. Pappenheimer bodies seen following splenectomy in patients without haematological disease are composed of ferritin. Whereas Pappenheimer bodies seen in pathological conditions like sideroblastic anaemia are also composed of iron laden mitochondria and phagosomes.
Pappenheimer bodies are seen in sideroblastic anaemia and haemolytic anaemia. The spleen clears Pappenheimer bodies. Splenectomy is associated with an increase in Pappenheimer bodies. The increase is more pronounced in patients with haemolytic anaemia and sideroblastic anaemia. Cells containing Pappenheimer bodies can be confused with late reticulocytes. Prussian blue stain, which is not taken up by reticulocytes, is helpful in differentiating the two. Pappenheimer bodies can also cause a false elevation of platelet counts when performed with electronic counters.
There is an intererting article about the history of Pappenheimer bodies published in The American Journal of Haematology (Am. J. Hematol 75:249;2004)
Auer rods are needle shaped azurophilic intracytoplasmic inclusion bodies described by John Auer in 1906. They are 0.1-2μ wide and 3-6μ long and are formed by fusion of lysosomes. They contain peroxidase and lysosomal enzymes. They are seen in acute leukaemia (myeloblastic, promyelocytic, monomyelocytic and monocytic), myelodysplastic syndromes (RAEB-2) and chronic monomyeloid leukemia. Myelodysplastic syndromes, according to the WHO classification are disorders cytopenias and <20% blasts in the bone marrow. Patients with 10-19% blasts are classified as RAEB–2. Documenting Auer rods is important in examination of bone marrow smears of patients suspected to have MDS as a patient is classified as RAEB-2 even with <10% blast if Auer rods are present. Of the Romanovsky stains there are reports of Leishman’s stain being suboptimal for staining for Auer rods. The prognosis of patients with myelodysplastic syndromes worsens with increasing blasts. Patients with Auer rods have a worse prognosis than similar patients without Auer rods (Am J Clin Pathol 124:191; 2005). A lymphoid leukaemia can be excluded in patients with Auer rods.