ADVANCED BLOOD CELL ID: PERIPHERAL BLOOD FINDINGS IN MULTIPLE MYELOMA

Educational commentary is provided for participants enrolled in program #259- Advanced Blood Cell Identification. This virtual blood cell identification program includes case studies with more difficult challenges. To view the blood cell images in more detail, click on the sample identification numbers underlined in the paragraphs below. This will open a virtual image of the selected cell and the surrounding fields. If the image opens in the same window as the commentary, saving the commentary PDF and opening it outside your browser will allow you to switch between the commentary and the images more easily. Click on this link for the API ImageViewerTM Instructions.

Learning Outcomes

After completing this exercise, participants should be able to:

• Identify morphologic characteristics of immature granulocytes. • Describe morphologic abnormalities in leukocytes and erythrocytes associated with multiple myeloma.

Case Study

A 65 year old male complained of fatigue during a routine physical. His CBC results are as follows: WBC=3.9 x 109/L, RBC=2.48 x 1012/L, Hgb=8.2 g/dL, Hct=24.7%, MCV=99.5 fL, MCH=32.9, MCHC=33.0 g/dL, RDW=19.8 %, Platelet=28 x 109/L.

Educational Commentary

The cells selected for identification and discussion in this exercise were seen in the peripheral blood smear of a 65 year old man diagnosed with multiple myeloma. Multiple myeloma, also known as plasma cell myeloma, is a hematologic disorder that originates in the bone marrow and is associated with an increase in marrow plasma cells, overproduction of monoclonal immunoglobulin in serum and/or sometimes urine, and lytic bone lesions that result commonly in back pain.

Cell ABI-01 is a plasma cell. Plasma cells, or plasmacytes, are mature B lymphocytes that produce and secrete immunoglobulin. Plasma cells vary in size and are usually round or oval. Nuclei in these cells are also generally round or oval and are typically eccentrically located within the cell. The nuclear chromatin is dense and clumped and often appears as a “clock face” or “spoke wheel” pattern. Nucleoli are generally not present. Depending on nuclear size, the cytoplasm may be moderate to abundant and is characteristically deep blue. A perinuclear halo (also called a hof) is a classic feature of plasma cells. This lightly stained area or clear zone adjacent to the nucleus represents the Golgi body, a cellular organelle that functions to package protein, in this case, immunoglobulin. The hof in this particular cell is not as prominent as is sometimes seen.

American Proficiency Institute – 2016 1st Test Event

ADVANCED BLOOD CELL ID: PERIPHERAL BLOOD FINDINGS IN MULTIPLE MYELOMA (cont.)

Plasma cells are not normally present in the peripheral blood. They generally constitute only about 1% of normal bone marrow cells. However, in conditions such as multiple myeloma, it is not unexpected that their numbers are increased in the peripheral blood. A bone marrow examination would undoubtedly also show increased plasmacytes.

The cell chosen for ABI-02 is a normal lymphocyte. Lymphocytes are variable in size, but this cell is a nice example of a small lymphocyte. Small lymphocytes like this cell are usually round or oval and have nuclei that are also round or oval, although sometimes slight nuclear indentations may be seen. The chromatin is dense and clumped. Nucleoli may be present in some lymphocytes, but are typically not visible. The cytoplasm in small lymphocytes is scanty and blue.

The cell shown in ABI-03 is a band neutrophil. Bands are medium-sized cells and, as with plasma cells and normal lymphocytes, are round or oval. These cells are distinguished by their nuclear shape, which may appear like a band or as the letters C or U. The nucleus is always thick and never constricts to just a thin filament. The nuclear chromatin in band cells is condensed and clumped. Chromatin and parachromatin may be seen in the bridge between lobes. The cytoplasm is packed with numerous specific or secondary granules that are pink or tan.

Red blood cells demonstrating rouleaux have been selected for ABI-04. Rouleaux formation is not normally seen in thin areas of a blood slide. Artifactual rouleaux is a common finding on almost any blood smear if the area examined is in the thick portion of the smear.

Rouleaux refers to the arrangement of four or more red blood cells in a linear formation. Early microscopists referred to this unusual pattern as a “stack of coins.” The central pallor of the erythrocytes may sometimes be seen. However, note that although rouleaux is present in every field of view for this case study, no central pallor is evident in any of the red blood cells that have formed rouleaux. It is notable that very few of the erythrocytes in any of the fields of view for this case have nice areas of central pallor. The massive amount of immunoglobulin generated in multiple myeloma sometimes makes it difficult to prepare a good smear.

The large quantity of protein secreted in multiple myeloma contributes to rouleaux formation. Generally, red blood cells are repelled by negative charges. Plasma proteins, such as immunoglobulin, coat the surface of erythrocytes, reducing the negative charges and allowing the cells to stack together in rows and form rouleaux. Rouleaux should not be mistaken for agglutination, in which red blood cells have a tendency to clump rather stack.

American Proficiency Institute – 2016 1st Test Event

ADVANCED BLOOD CELL ID: PERIPHERAL BLOOD FINDINGS IN MULTIPLE MYELOMA (cont.)

The cell chosen for ABI-05 is an abnormal or immature plasma cell. Sometimes such a cell is defined as a “myeloma cell.” They may represent atypical plasma cells, plasmablasts, or proplasmacytes. These cells are often larger than normal plasma cells and are usually round or oval. This example probably became slightly elongated during smear preparation. Likewise, the normally round or oval nucleus has been stretched, although it still appears eccentrically located in the cell. The chromatin is not as dense and clumped as the mature plasma cell shown as cell ABI-01, and parachromatin is evident. The cellular margins are also uncharacteristically frayed. The deep blue cytoplasm and clearly recognized hof still define this cell as a type of plasma cell.

Some participants misidentified the cell shown in image ABI-05 as a hairy cell. A careful review of this cell, as well as surrounding cells in the fields of view, indicate several morphologic features that suggest this cell is not a hairy cell. Note that in this particular cell the nucleus shows frayed margins as does the cytoplasm. In true hairy cells, only the cytoplasm displays any of the fine, “hair-like” projections commonly associated with these cells. Fraying around the nucleus suggests artifactual aberrations that formed during preparation of the blood smear. Likewise, hairy cells do not have the cytoplasmic clearing, or hof, seen in plasma cells and often do not have the more intense blue cytoplasm also visible in plasma cells. Finally, the appearance of marked red blood cell rouleaux is not a finding seen in hairy cell leukemia and should suggest that a the cell in question is a plasma cell and not a hairy cell.

ABI-06 is another example of an abnormal or immature plasma cell. It was chosen to emphasize the variety of morphologic characteristics that are possible when the plasma cells are malignant, as in this case of multiple myeloma. Note that in this cell, the chromatin is even more loose and open then in the previous cell (ABI-05) and a prominent nucleolus is visible, indicating that this cell is immature and possibly a plasmablast. The cytoplasm is a deep blue as is expected in an immature cell, but the perinuclear clear zone suggest that this cell is from the plasma cell lineage. Although none were observed on this smear, other abnormal morphologies possible in malignant plasma cells include immunoglobulin inclusions as well as binucleated, multinucleated, and mitotic cells.

The last cell annotated in this series, ABI-07, is a promyelocyte. While it is not expected to see immature granulocytes, such as this cell and the band cell in ABI-03, it is important to be vigilant when reviewing peripheral blood smears so that all cells and abnormalities are identified.

Promyelocytes are large cells. The cells are round to oval in shape. There is a high nuclear to cytoplasmic ratio and the nucleus is also round or oval. Although not obvious in this cell, the chromatin is more open with minimal clumping; nucleoli may be apparent in promyelocytes. The cytoplasm is blue

American Proficiency Institute – 2016 1st Test Event

ADVANCED BLOOD CELL ID: PERIPHERAL BLOOD FINDINGS IN MULTIPLE MYELOMA (cont.)

with characteristic granules. These nonspecific, primary, or azurophilic granules are frequently numerous and appear violet or purple.

Multiple Myeloma

Multiple myeloma is a hematologic bone marrow disorder most often associated with older adults, as in this case study patient. Patients also present with anemia, as noted in this exercise with the patient’s hemoglobin of 8.2 g/dl and hematocrit of 24.7%. Thrombocytopenia often develops as the disease progresses. The reported platelet count for this patient was 28.0 x 109/L. Evaluating the fields of view for all the cells selected in this testing event confirms the thrombocytopenia. Most likely the patient’s bone marrow is packed with plasma cells affecting the production of red blood cells and platelets.

In multiple myeloma, plasma cells may also be seen in the peripheral blood and erythrocyte rouleaux may be striking, as in this patient. The majority of patients with multiple myeloma have elevated monoclonal immunoglobulin in their serum or urine, a result of the increased marrow plasma cells. Most patients have a progressive disease, but newer treatment advances are extending survival and improving prognosis for these patients.

Summary

Both the increase in bone marrow plasma cells and the over secretion of associated immunoglobulin contribute to the abnormal peripheral blood findings seen in this case study patient. Although it is not characteristic to see immature granulocytes in multiple myeloma, the presence of these cells is not surprising given that the patient’s bone marrow is likely stressed by the elevated number of plasma cells. The medical laboratory professional assists in the accurate diagnosis of this condition by recognizing key morphologic findings consistent with multiple myeloma.

References

1. Glassy EF. Color Atlas of Hematology. Northfield, IL: College of American Pathologists; 1998.

2. Gulati G, Caro J. Blood Cells: An Atlas of Morphology with Clinical Relevance. Chicago, IL: ASCP Press; 2007.

3. Kjeldsberg CR, Perkins SL. Practical Diagnosis of Hematologic Disorders. Vol. 2: Malignant Disorders. 5th ed. Chicago, IL: ASCP Press; 2010.

American Proficiency Institute – 2016 1st Test Event