PMC5428180_01
(A) Peripheral blood smear shows leukocytosis with circulating blasts (thin arrow), promonocytes (thick arrow), monocytes, and dysplastic granulocytic cells (hyposegmented neutrophils, arrow head). Inset shows eosinophilic myelocytes with abnormal coarse basophilic primary granules. (B) Bone marrow aspirate smear showing blasts cells, promonocytes, monocytes, and granulocytic cells with dysplastic features (hyposegmented neutrophils) (Wright stain, original magnification x1000). (C) Bone marrow biopsy shows infiltration with leukemic cells, many with irregular convoluted nuclear contour with prominent eosinophilic cells (hematoxylin-eosin, original magnification x600). Inset: Low-power bone marrow biopsy shows remarkably hypercellular marrow with extensive diffuse infiltration (hematoxylin-eosin, original magnification x40).
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The blasts were medium to large in size with fine chromatin and prominent nucleoli, some with irregular/convoluted nuclear contour (Figure 1A). Maturing myeloid cells comprised (28%) severe dysplastic features and included 2% eosinophils (Figure 1B). Bone marrow biopsy showed markedly hypercellular BM with diffuse infiltration by blasts (Figure 1C), positive for CD34, lysozyme, myeloperoxidase, and CD68, with partial positivity for CD117.
Flow cytometry analysis of bone marrow aspirate at presentation revealed approximately 56% blast cells (green gate). Blasts are positive for cMPO, CD117, CD13, CD33, and CD34, and the majority is positive for HLA-DR. FITC indicates fluorescein isothiocyanate.
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Flow cytometry analysis revealed approximately 56% myeloid blasts with moderate CD45 and expressing CD34, cMPO, CD33, CD13, and CD9, and the majority was positive for CD117 and HLA-DR, with partial expression of CD15 (on approximately 35% of the cells) (Figure 2).
Interphase FISH and cytogenetic studies showing an inv(16). (A) Interphase FISH; CBFB Break Apart FISH Probes are used to detect inv(16); centromeric end 5' is labeled with spectrum orange and telomeric end 3' is labeled with spectrum green. The normal homologue of chromosome 16 shows a fusion (yellow), the abnormal chromosome 16, with inversion shown in orange and green signals apart from each other. (B) Partial karyotype shows normal chromosome 16 and inv(16) indicated with arrow. FISH indicates fluorescent in situ hybridization.
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This was confirmed by conventional karyotype which showed inv(16)(p13.1q22), concluding the diagnosis of AML with inv(16)(p13.1;q22) CBFB:MYH11 (Figure 3).
(A). Bone marrow aspirate smear shows different stages of granulocytic cells, normoblasts, and mast cells (arrowed) (Wright stain, original magnification x1000). (B) Cytologic abnormalities of mast cells. (a to c), Atypical mast cell type 1 with eccentric nucleus and hypogranular cytoplasm; (d) atypical mast cell type 1, spindle form; (e to h) atypical mast cell type II with kidney shape, bilobed nuclei with mature chromatin and hypogranular cytoplasm; (i to k) atypical mast cell type II with bilobed or multilobed nuclei with hypogranular cytoplasm and more fine immature chromatin (promastocyte); (l) atypical mast cell type II with fine chromatin and agranular cytoplasm (Wright stain, original magnification x1000.
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However, the BM aspirate showed the presence of morphologically atypical MC comprising approximately 2% of the total cells, mostly with irregular nuclear contour (kidney-shaped, bilobed, or multilobed nuclei), pale cytoplasm with cytoplasmic hypogranulation or irregular metachromatic granule distribution, some with fine nuclear chromatin (promastocyte morphology), together with some cells showing eccentric nucleus or spindle shape (Figure 4A and B).
(A) Bone marrow biopsy shows perivascular collections of mast cells (circled) (hematoxylin-eosin, original magnification x100). Inset: Many of the mast cells are of elongated spindle form (hematoxylin-eosin, original magnification x1000). (B) Bone marrow biopsy shows intertrabecular aggregate of mast cells (hematoxylin-eosin, original magnification x400). Inset: Some of the mast cells show kidney-shaped nucleus (hematoxylin-eosin, original magnification x1000. (C) Immunohistochemistry on bone marrow biopsy. The mast cells are positive for CD117, tryptase, and CD25, with no significant staining for CD2 (x200).
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CD117, CD68, and CD25. CD2 immunostain appeared negative (Figure 5A to C).