Myeloid Sarcoma: Clinicopathologic, Cytogenetic, and Outcome Analysis of 21 Adult Patients

Myeloid sarcoma (MS) is a neoplasm of immature granulocytes, monocytes, or both involving any extramedullary site. Twenty one patients with MS at diagnosis who were treated at King Hussein Cancer Center in Jordan were included in this retrospective study with a male to female ratio of 2？:？1. The most common site was the reticuloendothelial system. The most common morphology subtype was M2 (38%) and the most frequent chromosomal abnormality was trisomy 8. Twenty patients received induction chemotherapy; only 14 (70%) achieved complete remission. Median survival time was 24.7 months for the whole group and 58.6 months for patients who underwent allogenic bone marrow transplant. This paper showed that MS has frequent M2 morphology, carries chromosomal aberrations other than t(8;21), and requires aggressive therapy as a front line approach. 1. Introduction Myeloid sarcoma (MS) is a tumorous aggregate of malignant immature granulocytes, monocytes, or both involving any extramedullary site. Although first described by Burns [1] in 1811, it was King [2] in 1853 who coined the term chloroma based on the green color of the tumorous mass attributable to the enzyme myeloperoxidase. MS may occur de novo in the absence of any past history or current bone marrow involvement by acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), or myeloproliferative disorder (MPD) [3]. This primary form of MS is relatively rare. On the other hand, secondary MS (defined as the occurrence of MS manifestation in patients with previous or current bone marrow involvement by AML, MDS, or MPD) occurs in approximately 1.4% to 9% of patients with AML [4, 5]. MS is frequently mistaken for non-Hodgkin's lymphoma, small round cell tumors (neuroblastoma, rhabdomyosarcoma, Ewing sarcoma, and medulloblastoma), and undifferentiated carcinoma, which may cause misdiagnosis in about 50% of cases when immunohistochemistry is not used [6]. The present study was designated to evaluate the lineage differentiation of neoplastic cells in MS by immunohistochemistry and to correlate the results with the clinicopathological features, cytogenetics, and treatment outcomes. 2. Patients and Methods Twenty one adult (18 years of age or more) patients with a histologic diagnosis of MS at presentation, who were managed at KHCC in Jordan between 2004 and 2008, were included in the present study. The study was approved by the institutional review board at KHCC. The charts of these patients were reviewed retrospectively for data collection including age, sex, anatomic site of involvement,