Objective:

To report a rare case of pediatric CNS myeloid sarcoma with erythroid differentiation, emphasizing the diagnostic challenges and molecular characteristics that complicate its identification.

Key Findings:

• The patient exhibited diffuse parenchymal brain infiltration without mass formation, indicating a unique presentation of the disease.
• Cerebrospinal fluid analysis revealed a significant population of immature erythroid cells, which is critical for diagnosis.
• RNA sequencing confirmed the presence of an NFIA::CBFA2T3 fusion, a genetic alteration associated with myeloid sarcoma with erythroid differentiation.

Interpretation:

The case underscores the critical role of molecular testing in diagnosing myeloid sarcoma with erythroid differentiation, particularly in cases lacking bone marrow involvement, which can lead to misdiagnosis.

Limitations:

• The rarity of the condition limits broader applicability of findings, suggesting a need for more extensive studies.
• The case is based on a single patient, which may not represent all instances of the disease, highlighting the necessity for further research.

Conclusion:

This case illustrates the critical role of advanced molecular techniques in diagnosing complex hematological malignancies in pediatric patients, emphasizing the need for awareness and further investigation in similar cases.