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Patient 1 bone marrow aspirate and trephine biopsy. (A, B) Bone marrow aspirate smear (Wright-Giemsa, x400, x1,000) is notable for numerous mast cells intermixed with myeloblasts. Degranulated mast cells are interspersed throughout the bone marrow aspirate smear. (C) The bone marrow biopsy (H&E, x100) demonstrates hypercellular marrow for age (90% cellularity). (D) Approximately 50% of the cellularity is composed of mast cells with oval nuclei, and hypogranulated cytoplasm (H&E, x400). Blast elements and other marrow elements are scattered throughout. (E) CD117 immunostain (x400) highlights abundant mast cells. (F) Mast cell tryptase immunostain (x400). (G) CD34 immunostain (x400) highlights blast elements, comprising >20% of non-mast cell cellularity. (H) CD25 immunostain (x400) is positive in the neoplastic mast cells.
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Bone marrow biopsy (Figure 1) demonstrated markedly hypercellular marrow (90% cellular), with approximately 50% of the cellularity composed of pale, round, degranulated mast cells scattered and in clusters, aberrantly expressing CD25.
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