en Pediatric Pediatric case report case report Malignant histiocytosis (MH) is a rare hematologic malignancy, especially in the first decade of life. The disease is clinically characterized by fever, hepatosplenomegaly, lymphadenopathy, pancytopenia and jaundice, and histologically by systemic proliferation of malignant histiocytes and hemophagocytosis. The prognosis is poor and often the diagnosis is not made before death. Because of the rarity of this disease, it is unusual for practitioners to diagnose it by bone marrow aspiration (BMA) alone 79 83 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-469&slc_lang=en&sid=1 A BANIHASHEM 20031947532846005478 20031947532846005478 Yes From the Departments of Pediatrics Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Islamic Republic of Iran. T GHIASSI 20031947532846005479 20031947532846005479 No From the Departments of Pathology, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Islamic Republic of Iran. S ZABIHYAN 20031947532846005480 20031947532846005480 No