<![CDATA[Background: Myeloid sarcoma (MS) is a rare extramedullary tumor composed of myeloblasts or immature myeloid cells. It is often associated with acute promyelocytic leukemia (APL), which is a subtype of acute myeloid leukemia (AML), but rarely presents as the initial manifestation of the disease, particularly in children. Diagnosing MS is challenging due to its rarity and clinical resemblance to other malignancies. Early identification and proper diagnostic evaluation are crucial for accurate diagnosis and timely intervention. Case Presentation: We report a 2-year-old girl presenting with a history of a cranial mass and bilateral orbital involvement, initially suspected as neuroblastoma. Laboratory findings revealed anemia, leukocytosis with increased immature granulocytes. Bone marrow aspirate analysis demonstrated 40% promyelocytes, consistent with APL. Fine needle aspiration biopsy (FNAB) of the mandibular lesion showed malignant cells, and immunocytochemical staining was positive for myeloperoxidase (MPO), confirming the diagnosis of MS. The patient was treated with all trans retinoic acid (ATRA) and the chemotherapy agent methotrexate combined with daunorubicin, leading to a favorable response.Conclusions: This case highlights the importance of considering myeloid sarcoma in the differential diagnosis of orbital masses in children, especially when accompanied by hematologic abnormalities. Early recognition and appropriate diagnostic workup, including bone marrow analysis and immunocytochemistry, are essential to establish the diagnosis of APL with extramedullary involvement and to initiate prompt, targeted therapy.]]>
