Greatly increased giant platelets mimicking blasts in flow cytometric analysis from a patient with primary myelofibrosis

Excerpt

A bone marrow specimen was received for confirmatory flow cytometric analysis for an increased blast count detected by outside flow cytometry on a 69-year-old male with a history of JAK2-positive primary myelofibrosis. A large, CD45-dim population was noted on flow cytometry (Fig. 1(A), blue), mimicking blasts. However, blasts were not increased on the hypocellular/hemodiluted bone marrow aspirates after thorough morphologic review. Instead, numerous giant platelets were identified (Fig. 1(B)), with a spectrum of size (Fig. 1(C)). Further flow cytometric immunophenotyping revealed this population was positive for CD41 (Fig. 1(D)), CD31 (not shown), and CD61 (not shown), and it was negative for CD34 (Fig. 1(D)) compared to the internal CD34-positive myeloblasts (Fig. 1(D), red). It was also negative for other myeloid-, lymphoid-, and plasma cell-associated markers (not shown).

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