Acute Myeloid Leukemia with Hemophagocytosis: Diagnostic Cues and Potential Pitfalls.

Hemophagocytosis is the process of phagocytosis of erythrocytes or other hematopoietic precursors by histiocytes or macrophages. Increased histiocytic activity may be observed in infections, inflammation, bone marrow hyperplasia, ineffective hematopoiesis, malignancies, as well as in hemophagocytic lymphohistiocytosis (HLH). Here we present two challenging cases of acute myeloid leukemia (AML) with associated hemophagocytosis, one in which hemophagocytosis provided a diagnostic cue and another in which extensive HLH obscured the underlying AML. The first case highlights the characteristic morphologic (leukemic blasts with erythrophagocytosis) and immunophenotypic findings (high side scatter and bright HLA-DR expression) observed in AML with t(8;16). The second case highlights the importance of careful bone marrow examination to rule out an underlying malignancy in children presenting with HLH, as the diagnosis and treatment of primary malignancy is crucial in successful management. The second case also shows an uncommon presentation of AML with concomitant EBV-associated HLH. A high index of suspicion for malignancy based on clinical history and careful bone marrow examination led us to reach the definitive diagnosis in a timely manner and allowed for optimal patient management.