EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION Educational commentary is provided through our affiliation with the American Society for Clinical Pathology (ASCP). To obtain FREE CME/CMLE credits click on Continuing Education on the left side of the screen. Learning Objectives: After completion of this testing event, the participant will be able to: • Describe morphologic features of normal peripheral blood leukocytes and platelets. • Identify morphologic abnormalities in erythrocytes and leukocytes associated with Waldenström's macroglobulinemia. The patient presented in the case study for this testing event has been diagnosed with Waldenström's macroglobulinemia. The images for review represent not only normal leukocytes and platelets, but also several abnormalities in red blood cells that may be seen in this condition. The photographs also include a leukocyte (plasma cell) that is not normally viewed in the peripheral blood. BCI-15 depicts a band (stab) neutrophil. Band cells are the earliest precursors of neutrophil maturation that can be normally visualized in the peripheral blood. They characteristically have a nucleus that is shaped like the letters “C” or “U”. The chromatin is clumped and dense. The cytoplasm in band cells contains many specific granules that stain tan, pink, or violet. Picture BCI-16 shows a polychromatophilic erythrocyte. This cell actually represents the stage of red blood cell maturation just prior to the mature erythrocyte, the reticulocyte. The reticulocyte stage begins just after the nucleus has been extruded by the erythrocyte. A small amount of RNA (ribonucleic acid) is still present in the cells and therefore the cell appears blue-gray when Wright’s stain is used. The term polychromasia also describes the presence of these cells on a peripheral blood smear. Many times, reticulocytes appear larger than normal erythrocytes, though that is not the case in this particular example. Reticulocytes normally mature for about 48 hours in the bone marrow and another 24 hours once released into circulation. The appearance of polychromatophilic cells in the peripheral blood indicates the bone marrow is trying to compensate for a decrease in oxygen carrying capacity. Seeing polychromasia in this case study patient is not unexpected given the very low red blood cell count, hemoglobin value, and hematocrit level. American Proficiency Institute – 2006 3rd Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.) Picture BCI-17 illustrates an abnormal distribution pattern in the erythrocytes called rouleaux. Early scientists likened this unusual formation to a “stack of coins.” Rouleaux occurs when four or more red blood cells are arranged in a linear pattern. It is important to note, however, that artifactual rouleaux can be seen in the thick area of almost any peripheral blood smear. True rouleaux is found in the thin portion of a blood film. BCI-17 shows rouleaux in an acceptable area of the slide and is consistent with the diagnosis of this patient’s condition. Normally, erythrocytes are repelled by net negative changes and do not stick to each other. However, when increased amounts of plasma proteins coat the surface of erythrocytes, this negative change is neutralized and rouleaux formation occurs. Many conditions can cause a significant increase in plasma proteins, including inflammation, infection, and monoclonal gammopathies, such as Waldenström's macroglobulinemia. Finally, it is important that rouleaux not be confused with agglutination. In agglutination, erythrocytes form a lattice, network or clump rather than a stack or chain as in rouleaux. Agglutination formation is specifically associated with the production of antibodies. Image BCI-18 represents a normal mature lymphocyte. Though this example shows a small lymphocyte, it is important to recognize that these cells are quite variable in size. In small lymphocytes such as this one, the cytoplasm is very blue and often scanty. Nuclei may be round, oval, or slightly indented. The nuclear chromatin is dense, clumped, and stains a deep purple. The cells identified in BCI-19 are normal peripheral blood platelets. Platelets are commonly called cells, but technically are not cells because they have no nuclei. However, they do originate from nucleated cells in the bone marrow called megakaryocytes and represent cytoplasmic fragments of these cells. The platelets shown in this image are typical. They are small, and the cytoplasm stains blue while the granules stain purple-blue. Platelet shapes can vary, but they are most often round or oval. American Proficiency Institute – 2006 3rd Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.) A nucleated red blood cell is featured in BCI-20. Nucleated red blood cells are immature cells that have not yet expelled their nuclei. Normally, nucleated erythrocytes are seen only in bone marrow smears. Their presence in the peripheral blood indicates abnormal or accelerated erythropoiesis. Again, the patient in this testing event is very anemic, so the presence of nucleated red blood cells is not an unexpected finding. Nucleated erythrocytes represent specific stages in the red blood cell maturation continuum, but the particular stage does not need to be identified. However, it is important to report the number of nucleated red blood cells counted per 100 white blood cells when performing a differential cell count. In this situation, 8 nucleated erythrocytes were counted per 100 white blood cells. The nucleated erythrocyte shown in this picture is typical of those seen in the peripheral blood. Note the clumped, dense chromatin and scanty, blue-gray cytoplasm. Sometimes nucleated red blood cells and small lymphocytes, as shown in BCI-18, may be confused. In such situations, the chromatin structure is very helpful in classifying the cell. Notice how the nuclear chromatin in the lymphocyte, though dense, has light and dark staining areas. In contrast, the nucleated erythrocyte has a chromatin pattern that is so dense it is really feature-less. A plasma cell is shown in BCI-21. Although the bone marrow, spleen, and lymph nodes are more frequently involved in Waldenström's macroglobulinemia, it is not surprising to see plasma cells in the peripheral blood of this patient. Normally, plasma cells should not be seen in the peripheral circulation, and their presence does indicate an abnormal condition. Plasma cells characteristically have nuclei that are round or oval and often located eccentrically within the cell. The chromatin is very clumped and stains a dark purple. Plasma cells are generally medium sized, with moderate to abundant, intensely blue cytoplasm. A prominent clear zone or lightly stained area can be seen adjacent to one side of the nucleus. This clearing represents the Golgi body, a cellular organelle that functions in packaging protein, in this case, immunoglobulin. Note that plasma cells can also be identified in BCI-16, BCI-18, BCI-19, and BCI-20. The differential cell count performed on this patient’s smear indicated 24% plasma cells. American Proficiency Institute – 2006 3rd Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.) An abnormal production of monoclonal immunoglobulin characterizes Waldenström's macroglobulinemia. This disorder represents the uncontrolled proliferation of not only plasma cells, but also lymphocytes and cells called plasmacytoid lymphocytes. The plasma cells secrete excessive amounts of only one type of immunoglobulin, in this case, IgM. Additional laboratory testing on the patient presented in this case included serum protein electrophoresis and a bone marrow exam. These tests confirmed the diagnosis of Waldenström's macroglobulinemia. The electrophoresis showed an IgM monoclonal peak and the bone marrow revealed a diffuse infiltrate of plasma cells, plasmacytoid lymphocytes, and lymphocytes. In summary, Waldenström's macroglobulinemia is a disorder that results in the abnormal production of plasma and related cells. The malignant plasma cells generate increased amounts of only one type of immunoglobulin. Several characteristic peripheral blood findings are associated with this condition, and include rouleaux of red blood cells as well as the presence of plasma cells. Other nonspecific peripheral blood features indicate the overall hematopoietic stress associated with Waldenström's macroglobulinemia, such as nucleated red blood cells and polychromasia. In the morphologic review of a peripheral blood smear from a patient with Waldenström's macroglobulinemia, it is important to distinguish the malignant plasma cells from normal lymphocytes and from nucleated red blood cells. A careful review of cell size, cytoplasmic features, and nuclear chromatin structure is essential when classifying blood cells. © ASCP 2006 American Proficiency Institute – 2006 3rd Test Event .