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case_images: Morphology and cytochemistry of peripheral and bone marrow smear of tumor cells. Basophilic precursors with medium-size, round nucleus and moderately basophilic cytoplasm containing a variable number of coarse basophilic granules (a). Marrow smear showed these atypical basophils were positive for toluidine blue (b) and negative for peroxidase (c).
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case_images: A peripheral blood film showed that 51% of cells had the characteristics of basophils, of which 22% resembled to basophilic precursors, with a medium-sized, round nucleus and moderately basophilic cytoplasm containing a variable number of coarse basophilic granules (Figure 1a), which were positive for toluidine blue (Figure 1b) and negative for peroxidase (Figure 1c). 
case_images: Morphology and immunohistochemistry of bone marrow biopsy. Biopsy showed a hypercellularity BM. The tumor cells shared similar histology morphology characteristics with the myeloid blast cells. And a large proportion of unexpected small round cells with sparse basophilic granules was discovered (a). Myeloblast showed positive for CD34 (b). Immunostaining revealed there were more than 30% of cells strongly positive for CD117 (c).
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case_images: Bone marrow biopsy revealed a large proportion (more than 30%) of unexpected small round cells with sparse granules (Figure 2a). Immunohistochemistry (IHC) revealed that 10% were CD34-positive myeloblasts (Figure 2b), and more than 30% of the cells were most likely a mastocytic differentiation, because they showed strong expression of CD117 (Figure 2c) and were negative for CD25.
case_images: Immunophenotyping up on flow cytometric study in bone marrow aspiration demonstrated that the neoplastic cells were subsequently revealed to exhibit a bi-differentiation. Basophilic precursors accounting for 13.8%, expressing CD13 and CD33 (a); and mast cells accounting for 28.8%, strongly expressing CD117 and CD25 (b).
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case_images: In which group one accounting for 13.8%, expressing CD13 and CD33 (Figure 3a) resemble to basophilic precursors; and group two accounting for 28.8%, strongly expressing CD117 and CD25 (Figure 3b), demonstrating they were MCs lineage.  