Renal Extramedullary Hematopoiesis in Mast Cell Leukemia with Bone Marrow Fibrosis

Figure 3

Biopsy of the renal mass reveals extramedullary hematopoiesis and only few mast cell aggregates. (a, b) H&E stain shows extramedullary hematopoiesis. The single arrow in panel (a) illustrates megakaryopoiesis and double arrows in panel (b) indicate a mature group of erythroblasts. (c, d) Giemsa stain shows extramedullary granulopoiesis. Arrows in panel (c) depict segmented mature granulocytes, and arrows in panel (d) highlight intermixed atypical spindle-shaped mast cells. (e) Immunohistochemical staining for CD34 highlights vascular endothelium and shows absence of blasts. (f) Immunohistochemical staining for CD117 reveals mast cell hotspots. (g) Mast cell tryptase supports the presence of mast cells. (h) Only few mast cells show expression of CD25.

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