EDUCATIONAL COMMENTARY – CELL IDENTIFICATION

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Learning Outcomes Upon completion of this exercise, the participant will be able to: · Describe the morphologic features of normal peripheral blood leukocytes. · Identify the characteristic morphologic findings of immature .

Case History A 56 year old male, during a routine physical examination, complained of fatigue, weight loss, and frequent upset stomach. The CBC data was as follows: WBC = 60.5 x 109/L, RBC = 3.34 x 1012/L, Hgb = 9.8 g/dL, Hct = 29.1%, MCV = 87 fL, MCH = 29.3 pg, RDW = 23.4%, = 390 x 109/L. WBC Differential: = 72.8%, Lymphocytes = 7.8%, = 7.7%, = 3.0%, = 8.7%. The histogram indicated a manual differential should be performed.

The photographs presented in this testing event represent both normal and abnormal leukocytes that may be associated with chronic myelocytic (myelogenous, granulocytic) (CML). As demonstrated in this case situation, CML often presents in an insidious manner and is diagnosed only after the patient complains of and is evaluated for relatively nonspecific symptoms. Also characteristic of CML is the spectrum of immature and mature granulocytes that may be seen on a peripheral blood smear.

BCI-01 (below) shows a normal . The distinguishing feature of eosinophils are the many red- orange cytoplasmic granules. The nuclear chromatin is dense, clumped, and stains purple.

American Proficiency Institute – 2005 1st Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.)

The cell illustrated in BCI-02 is a . are not normally seen in the peripheral blood. However, in this case study, the patient has been diagnosed with CML, so it is not unexpected that a metamyelocyte is present. These cells characteristically have a nucleus that is barely indented or shaped like a kidney bean. The nuclear chromatin is clumped and condensed. Pink, tan, or violet specific granules fill the cytoplasm.

BCI-03 depicts a normal segmented . Note the characteristic nuclear segmentation. Neutrophils typically have 2-5 lobes connected by thin strands of chromatin. It is difficult to appreciate any thin filaments of chromatin in the cell shown in this picture, but there is definite constriction of the chromatin into segments. This constriction is more obvious when this cell is compared to the metamyelocyte in BCI-02 and the band neutrophil in image BCI-04. The chromatin is also coarsely clumped and dense, indicating a mature cell. Neutrophils have numerous small cytoplasmic granules that normally stain pink, tan, or violet.

A band or stab neutrophil is shown in BCI-04. These cells represent the earliest precursors of neutrophil maturation that can normally be seen in the peripheral blood. Bands are characterized by a nucleus that is shaped like a sausage or the letters C or U. Note the lobes in this band are connected by a bridge and show no constriction as in the previously shown segmented neutrophil. The cytoplasm, however, contains numerous specific granules that stain pink, tan, or vi olet and is similar to that seen in segmented neutrophils. In addition, note the dense and clumped chromatin.

Band cells are sometimes referred to as “stab” cells. This term is derived from the German word for “staff” because the cells reminded early scientist, Victor Schilling, of a shepherd’s staff.

American Proficiency Institute – 2005 1st Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.)

Sometimes distinguishing bands from segmented neutrophils can be difficult. Furthermore, the identification of bands between laboratories often does not agree and is extremely subjective, even when guidelines and definitions are provided. Therefore, experts have questioned the clinical utility of reporting a relative band count.

BCI-05 shows a . Monocytes are large cells. Their cytoplasm is often abundant, blue-gray in color, and vacuolated, as shown in this cell. The cytoplasm frequently appears uneven and rough. Although not present in the cell shown here, cytoplasmic projections, resembling pseudopods, may be seen. The nuclei in monocytes may be round, kidney-shaped, oval, or lobulated. The chromatin is generally a lighter pink or purple color and is usually fine with minimal clumping.

BCI-06 is a . are not normally seen in the peripheral blood. But, given the diagnosis of this patient’s condition, it is not surprising to see this cell. Myelocytes represent the maturation stage immediately preceding metamyelocytes. In contrast to the metamyelocyte, the nucleus in a myelocyte is often round or oval in shape and is eccentrically located within the cell. The chromatin shows some clumping, but lighter areas of parachromatin may still be seen. Nucleoli are not usually evident. Often a hof, or clear area, is visible adjacent to the nucleus and represents the cell’s Golgi body. The specific pink, tan, or violet granules of neutrophils are first seen in the myelocyte stage. Darker purple, nonspecific, or primary granules may still be evident, as is the case in this cell. Features that characterize this particular cell as a myelocyte include the oval, eccentrically placed nucleus, chromatin that shows areas of clumping, and a dusting of fine, pink granules in the cytoplasm.

The cell identified in BCI-07 (below) is a blast. As with metamyelocytes and myelocytes, blast cells should not be seen in the peripheral blood. Likewise, few blasts will be identified in the early phases of CML, while other granulocytic maturation stages are more prominent. One indicator of the progression of CML to a more serious level is the increased number of blasts that are seen on the peripheral blood smear.

American Proficiency Institute – 2005 1st Test Event EDUCATIONAL COMMENTARY – BLOOD CELL IDENTIFICATION (cont.)

Blasts are generally large cells with a high nuclear to cytoplasmic ratio. The cytoplasm is a dark blue, scanty in amount, and contains no granules. The nucleus is oval or round in shape with a fine chromatin pattern. Sometimes, multiple prominent nucleoli are visible, especially in . Classification of the cell lineage of blast cells based only on Wright-stained morphology is often difficult because blast cells of different cell lines are so similar in appearance. Therefore, it is most important to identify an abnormal cell on a peripheral blood smear as a blast and use additional classification techniques to define cell type.

© ASCP 2005

American Proficiency Institute – 2005 1st Test Event