Dysplastic features seen in a patient with acute myeloid leukemia harboring the KTM2A-TET1 fusion gene

Excerpt

Pancytopenia was noted in an apparently healthy 38-year-old woman at a regular medical checkup. Laboratory tests showed a hemoglobin level of 10.5 g/dL, 10.4 × 10⁹/L platelets, and 1.1 × 10⁹/L leukocytes, including 3.0% blasts. A bone marrow examination revealed 49.1% peroxidase-positive blasts with delicate nuclear chromatin and basophilic cytoplasm. Some of the blasts had Auer rods (Fig. 1 panels A, E). Flow cytometric analysis revealed positivity for CD13, CD33, CD117, HLA-DR, CD34 and CD38 among the blasts. Her bone marrow showed trilineage dysplasia, including pseudo-Pelger-Huët anomaly (Fig. 1 panels A, arrow, B, C) and hypogranular neutrophils, multi-nucleation (Fig. 1 panel D, arrow) and abnormal chromatin clumping in erythroblasts and many megakaryocytes with separated nuclei (Fig. 1 panels F–L, arrow). Paraffin sections of bone marrow aspirate showed the proliferation of dysplastic CD42b-expressing megakaryocytes (Fig. 1 panels M, N). Because dysplasia was observed in > 50% of the erythroid and megakaryocytic lineage cells, she was tentatively diagnosed with acute myeloid leukemia with myelodysplasia-related changes (AML-MRC). A chromosomal analysis indicated 46,XX,t(10;11)(q22;q23) [7]/46,XX [1]. Reverse transcription polymerase chain reaction and sequencing analyses revealed the KMT2A (MLL)-TET1 fusion gene with KMT2A exon 9 fused to TET1 exon 9 in frame. Her final diagnosis was AML with t(10;11)(q22;q23) ; KMT2A-TET1. …