Acute myeloid leukemia mimicking mature lymphoid morphology

der(12) der(4) 12 ETV6 (12p13.2) 5'ETV6 3'ETV6 XL ETV6 BA probe 12 4 der(4) der(12)A 78-year-old man with no prior history of hematologic disorders presented with rapidly progressive dyspnea.The clinical examination was unremarkable.Initial laboratory investigations revealed anemia (76 g/L), thrombocytopenia (50 10 9 /L), and lymphocytosis (7 10 9 /L), with no eosinophilia.Blood smear review showed 35% blasts with atypical morphology, described as having a pseudo-lymphoid or mature lymphoid appearance, characterized by a distinct blocky chromatin pattern and occasional nucleoli, resembling mature lymphocytes (panel A, May-Grnwald Giemsa stain, 50 objective; and panel B, May-Grnwald Giemsa stain, 63 objective).Flow cytometry showed CD34 + blasts with CD13 + , CD33 + , CD117 + , CD15 + , TdT + , HLA-DR + , aberrant CD7 + , CD56 + , and negative for myeloperoxidase, surface/cytoplasmic CD3, CD19, and CD79a.Bone marrow aspirate showed 60% blasts, confirming acute myeloid leukemia (AML).Cytogenetic analysis revealed