Myeloid sarcoma of the orbit

The term, "myeloid sarcoma" refers to an extramedullary collection of immature myeloid cells. Rarely may it precede peripheral blood or bone marrow involvement, presenting as a diagnostic challenge. We report here a case of myeloid sarcoma in a 45 year-old man, who presented with a painful right orbital swelling of one month's duration. Fine needle aspiration cytology (FNAC) was performed and a diagnosis of myeloid sarcoma was offered. Subsequently, a complete blood count revealed 60% blasts in the peripheral blood and a diagnosis of acute myeloid leukemia (AML) was confirmed on bone marrow examination. This case is being documented to emphasise the utility of FNAC in making the correct diagnosis of this entity in a case of unsuspected AML.