PMC8801678_01
Peripheral blood (A,C,D) and bone marrow cytology (B) in a dog with B-cell chronic lymphocytic leukemia. On the first visit, cytology shows increased well-differentiated lymphoid cells in peripheral blood (A) and the bone marrow (B). Smudge cells (black arrows) are seen in peripheral blood (A). 22 days after initial treatment (C), cytology reveals lymphocytosis despite administration of prednisolone and chlorambucil. After 1 year of multimodality therapy with additional administrations of imatinib, leukocytosis and lymphocytosis are resolved (D) [(A-D): bar = 50 mum].
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F1
On peripheral blood smear, lymphocytosis with well-differentiated small lymphocytes and neutropenia were found (Figure 1A). Bone marrow aspirate cytology showed hypercellularity and infiltration with small-sized mature lymphocytes (Figure 1B); the percentage of lymphoid cells was 45%. The dog's leukocyte and lymphocyte counts did not resolve remarkably after 3 weeks of chlorambucil and prednisolone chemotherapy (Figure 1C). On day 386, WBC counts were within the normal range (15.41 x 109/L; reference range, 5.05-16.76 x 109/L), and lymphocyte counts were also within the normal range (3.2 x 109/L; reference range, 1.05-5.1 x 109/L; Figure 1D).
Flow cytometric scatter plots of peripheral blood from a dog with B-cell chronic lymphocytic leukemia at the time of diagnosis (A,B) and after 1 year of multimodality therapy (C,D). A template is used to identify lymphocytes (A,C). On the first visit, lymphocytes predominantly express the CD21 molecule (87.52% among lymphocytes), showing a B-cell origin (B). After 1 year of treatment, the number of lymphocytes expressing the CD21 molecule has decreased to normal [17.69% among lymphocytes, (D)] (FSC, forward scatter; SSC, side scatter).
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These results revealed a B-cell origin, which indicated B-cell CLL (Figures 2A,B). Approximately 1 year after starting treatment, flowcytometry was re-assessed for evaluating the current treatment response (Figure 2C). The number of cells expressing the CD21 molecule decreased from 24,678/muL at the first admission date to 704/muL (reference range, 85-350) showing a highly favorable response to medication (Figure 2D).