Contributed by Stacey Barron, MD and Sarah Gibson, MD
A 1-day old male was found to have pallor after birth. He was the product of an uneventful pregnancy and normal birth. He had no overt congenital anomalies/stigmata.
The complete blood count with differential from his first day of life demonstrated a severe leukocytosis with 94% blasts, a normocytic normochromic anemia, and a moderate-to-severe thrombocytopenia (Fig. 1).
The peripheral smear demonstrated numerous intermediate to large sized blasts with a high nuclear:cytoplasmic ratio, round to slightly irregular nuclear contours, finely dispersed chromatin with small nucleoli, and scant basophilic cytoplasm. No Auer rods were identified. (Figs. 2 and 3).
The bone marrow aspirate differential (Fig. 4) demonstrated 81% blasts with morphology similar to those found in the peripheral blood (Fig. 5).
A bone marrow biopsy revealed normocellular (80-90%) bone marrow with numerous large, immature-appearing cells with irregular nuclear contours admixed with normal hematopoietic elements (Fig. 6).
Cytochemical stains for sudan black, myeloperoxidase, and chloroacetate esterase/non-specific esterase double stain were performed on the bone marrow aspirate did not highlight the blasts (Fig. 7).
Immunohistochemical stains performed on the biopsy demonstrated that the blasts were positive for CD117 and negative for all other lymphoid, myeloid, erythroid, and megakaryocytic markers (Figs. 8, 9, 10, and 11).
Flow cytometric immunophenotypic studies performed on the bone marrow demonstrated an abnormal blast population, that comprised approximately 91% of total events, with the following immunophenotype: CD45 dim positive, CD34 negative, CD117 positive, CD13 dim/partially positive, CD33 positive, CD4 dim/partially positive, CD7 dim/partially positive, CD16 dim/partially positive, CD38 dim/partially positive, CD123 dim/partially positive, HLA-DR negative, myeloperoxidase negative, and TdT negative. The blasts may possibly express dim/partial glycophorin A; however, non-specific staining could not be excluded. The blasts are negative for the other myeloid, megakaryocytic, B-cell and T-cell lineage markers evaluated. (Figs. 12, 13, 14, 15, 16 and17)
Cytogenetic studies demonstrated a mosaic abnormal male bone marrow chromosome analysis with an apparently normal cell line represented by 12 cells and an abnormal pseudodiploid clone with a translocation between the short arm of the X chromosome and the long arm of one chromosome 6.
Fluorescence in situ hybridization (FISH) was negative for trisomies 4, 10, 17, and 21, and for the BCR/ABL1, MLL and ETV6/RUNX1 gene rearrangements in all of the interphase cells examined for each test (100%).