Auer rod Auer rods are elongated, bluish-red rods composed of fused lysosomal granules, seen in the cytoplasm of myeloblasts, promyelocytes and monoblasts and in patients with acute myelogenous leukemia.
	Toxic granulation Toxic granulation appears as dark blue-black granules in the cytoplasm of neutrophils. These granules are thought to be primary granules. Artifactual heavy granulation caused by poor staining is seen evenly spread throughout each cell and in all granulocytes, whereas toxic granulation is unevenly spread throughout the cytoplasm of certain cells. Large amounts of toxic granulation can give the neutrophil a bluish appearance.Toxic granulation is a stress response to acute infections, burns, and drug poisoning.
	Döhle bodies Döhle bodies appear as a small, light blue-gray staining area in the cytoplasm of the neutrophil. They are found in poisoning, burns, infections, and following chemotherapy.
	Rouleaux Rouleaux formation occurs when red blood cells form stacks or rolls. This is due to either an artifact (such as a result of not preparing the blood smear soon enough after placing the blood on the slide), or it may be due to the presence of high concentrations of abnormal globulins or fibrinogen. This formation of the red blood cells is found in multiple myeloma and macroglobulinemia.
	Acanthocyte Acanthocytes are red blood cells with irregularly spaced projections. These projections vary in width but usually contain a rounded end. They may be found in abetalipoproteinemia and certain liver disorders.
	Basophilic stippling Basophilic stippling appears as round, dark-blue granules in red blood cells on smears stained with supra vital stains such as brilliant cresyl blue. They may be observed in lead poisoning, exposure to some drugs, severe burns, anemias, or septicemia. The granules are precipitated ribosomes and mitochondria.
	Echinocytes (crenated red blood cells) Echinocytes are red blood cells with many blunt spicules, resulting from faulty drying of the blood smear or from exposure to hyperosmotic solutions. Pathological forms are associated with uremia. Echinocytes contain adequate hemoglobin and the spiny knobs are regularly dispersed over the cell surface, unlike those of acanthocytes.
	Elliptocytes Elliptocytes are red blood cells that are oval or cigar shaped. They may be found in various anemias, but are found in large amounts in hereditary elliptocytosis.
	Erythrocyte - polychromatophilic Polychromatophilia may be defined as increased numbers of immature peripheral red blood cells that have a blue-gray tint on Wright-stained smears, indicating the presence of cytoplasmic RNA. These cells are usually larger than normal. Many of these cells prove to be reticulocytes when stained with supravital stains such as brilliant cresyl blue. They appear under conditions of accelerated red cell production.
	Howell-Jolly bodies Howell-Jolly bodies are spherical blue-black inclusions of red blood cells seen on Wright-stained smears. They are nuclear fragments of condensed DNA, 1 to 2 µm in diameter, normally removed by the spleen. They are seen in severe hemolytic anemias, in patients with dysfunctional spleens or after splenectomy.
	Nucleated red blood cell Nucleated red blood cells, (nrbcs or normoblasts), represent the stages of a red blood cell before it matures. Cells of this stage are usually seen in newborn infants, and in patients with responses to hemolytic crises, such as in megaloblastic anemia and iron deficiency anemia. The average size of the normoblast is 7-12 µm in diameter. The cytoplasm is pink. The nucleus is pyknotic (a homogeneous blue-black mass with no structure).
	Pappenheimer bodies Pappenheimer bodies are iron containing granules in red blood cells that are seen because the iron is aggregated with mitochondria and ribosomes. They appear as faint violet or magenta specks, often in small clusters, due to staining of the associated protein. They are associated with severe anemias and thalassemias.
	Schüffner's granules Schüffner's granules may be found in cases of Plasmodium vivax. These granules appear as orange to pink colored stippling throughout the red blood cell. They may not be visible when normal staining times are used. To detect these granules, the smears should be allowed to stain for three hours
	Schistocyte Schistocytes are red blood cell fragments that result from membrane damage encountered during passage through vessels. They occur in microangiopathic hemolytic anemia, severe burns, uremia, and hemolytic anemias cause by physical agents, as in disseminated intravascular coagulation (DIC). They are sometimes referred to as "bite cells".
	Sickle cells Sickle cells are red blood cells that have become crescent shaped. When a person with sickle cell anemia is exposed to dehydration, infection, or low oxygen supply, their fragile red blood cells form liquid crystals and assume a crescent shape causing red cell destruction and thickening of the blood. Since the life span of the red blood cell is shortened, there is a temporary depression of red cell production in the bone marrow, and a subsequent fall in hemoglobin (and therefore the resultant anemia).
	Spherocytes Spherocytes are red blood cells that are almost spherical in shape. They have no area of central pallor like a normal red blood cell. Large spherocytes (macrospherocytes) are seen in hemolytic anemia. Small spherocytes (microspherocytes) are sometimes seen in severe burn cases. A variety of spherical forms are seen in hereditary spherocytosis. The cells depicted in this image are from a patient with hereditary spherocytosis.
	Stomatocyte Stomatocytes are red blood cells with an oval or rectangular area of central pallor, sometimes referred to as a "mouth". These cells have lost the indentation on one side and may be found in liver disease, electrolyte imbalance, and hereditary stomatocytosis.
	Target cells Target cells (codocytes) are erythrocytes with a central color spot in the area of pallor, resembling a target. They are seen in many hemolytic anemias, especially sickle cell, HbC disease, and thalassemia.
	Teardrop cells (dacrocytes) Teardrop shaped red blood cells are found in myelofibrosis and other myeloproliferative disorders, pernicious anemia, thalassemia, myeloid metaplasia, and some hemolytic anemias.
	Bacteria The image below illustrates a neutrophil with bacteria (Gram positive cocci). The major function of the neutrophil is to stop or retard the action of foreign matter or infectious agents. The neutrophil accomplishes this by moving to the area of inflammation or infection, phagocytizing (ingesting) the foreign material, and killing and digesting the material. Bacterial sepsis can result in a leukemoid reaction, involving white cell counts of 100,000 X 106/L (normal WBC=4,500 to 11,000 X 106/L), the presence of myelocytes, and the appearance of toxic granulation.This image was taken from a patient with Streptococcus pnemoniae infection.
	Giant platelet Giant platelets are platelets that are larger than 6.5 µm, or 75 to 100% the size of a normal red blood cell. A normal red cell is 6-8 µm in diameter. Normal platelets are approximately 1-4 µm, large platelets are approximately 4-6.5 µm.
	Platelet satellitosis Platelet satellitosis, (platelets encircling a neutrophil) occurs when a patient has a serum factor that reacts to the anticoagulant EDTA.
	Parasites The most common parasites encountered in the peripheral blood include malaria and babesia. Malaria is discussed in detail on the malaria link. Babesia are small ringlike protozoa within erythrocytes that resemble the ring stages of falciparum malaria. Most infections result from Babesia microti which is transmitted from wild feral deer mice to humans by the tick Ixodes dammini. It occurs in Nantucket Island, on coastal regions of the northeastern US, and in California. It has been found in France, Ireland, Scotland, and other European countries. The diagnosis of babesiosis can be made by demonstration of the ring-shaped parasites on Wright-Giemsa stained smears. Babesia are tiny rings with a minute chromatin dot and a minimal amount of cytoplasm. They may be round, oval, elongated, or ameboid. One or two chromatin dots, which stain dark purple, may be observed. More than one ring can be seen in an RBC. Tetrad forms may be noted and aid in positively identifying babesia.
	Yeast The image below illustrates a neutrophil with intracellular yeast. The major function of the neutrophil is to stop or retard the action of foreign matter or infectious agents. The neutrophil accomplishes this by moving to the area of inflammation or infection, phagocytizing (ingesting) the foreign material (in this case, the yeast), and killing and digesting the material.