Acute nonlymphocytic leukemia (M7 subtype) with erythrocytic internalization

Area of Science:

• Hematology
• Oncology
• Cell Biology

Background:

• Acute nonlymphocytic leukemia (ANLL) classification relies on morphology and immunophenotype.
• Megakaryoblastic leukemia (ANLL M7) is a subtype characterized by megakaryocytic differentiation.
• Understanding blast cell morphology is crucial for accurate diagnosis and treatment.

Observation:

• A unique case of ANLL M7 presented with erythrocytic internalization in approximately 3% of leukemic megakaryocytic precursors (LMP).
• Phagocytosis of erythrocytes by LMPs was confirmed using both light and ultrastructural microscopy.
• Internalized erythrocytes appeared to enter LMPs via cytoplasmic vacuoles potentially linked to the extracellular space.

Findings:

• The observed erythrocytic internalization suggests a possible role for rudimentary demarcation membrane system (DMS) equivalents in this process.
• This phenomenon challenges the specificity of phagocytosis as a marker for mononuclear phagocytic system cells.
• The presence of erythrocytic internalization can potentially lead to misclassification of undifferentiated blast cells.

Implications:

• This finding broadens the understanding of morphological variations in ANLL M7.
• It highlights the need for careful evaluation to avoid diagnostic errors in leukemia classification.
• Further research into the mechanisms of erythrocytic internalization in leukemia is warranted.