AML M7 Misdiagnosed as ALL.

Area of Science:

• Hematology
• Immunophenotyping
• Pediatric Oncology

Background:

• Hematogones are immature B lymphocytes normally found in bone marrow.
• Increased hematogones can mimic malignant blast cells in flow cytometry and histology.
• Distinguishing reactive hematogones from neoplastic blasts is crucial for accurate diagnosis and treatment.

Observation:

• A 16-month-old male was initially diagnosed with pre-B cell acute lymphoblastic leukemia (ALL) based on bone marrow flow cytometry.
• The flow cytometry showed a significant population of CD19 and CD10 positive 'blast' cells.
• Subsequent bone marrow biopsy revealed myeloid blasts (AML M7) expressing CD61 and Factor VIII, and negative for CD10/CD20, with some cells identified as hematogones.

Findings:

• The initial misdiagnosis stemmed from mistaking prominent hematogones for neoplastic blast cells.
• Flow cytometry findings in pediatric bone marrow require careful interpretation, especially concerning CD19 and CD10 expression.
• The case underscores the importance of integrating multiple diagnostic modalities, including histology and immunophenotyping, for definitive diagnosis.

Implications:

• This case highlights a critical diagnostic pitfall in pediatric hematology-oncology.
• Accurate identification of hematogones is essential to avoid unnecessary and incorrect chemotherapy for leukemia.
• Enhanced awareness and diagnostic criteria are needed to prevent misdiagnosis of hematogones as blast cells in young children.