1. Introduction

Myeloid Sarcoma (MS) constitutes a rare pathological condition of extramedullary manifestation of leukemic cells of primarily myeloid origins that destroy the normal tissue architecture at the site of origin. Presence of the enzyme myeloperoxidase (MPO), gives the tumors its characteristic green hue, leading to the term, 'chloroma' (Greek, Chloros, meaning green) coined by a British physician, A. Burns in 1811 [1, 2]. Alternatively, MS is also referred as, Granulocytic sarcoma or Myeloblastoma. In the majority of the cases, MS is associated with acute myeloid leukemia (AML), however, it may also manifest in non-leukemic individuals. In addition, MS has also been reported in cases of myeloproliferative neoplasms (MPN), or

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

myelodysplastic disorders (MPD) [3, 4]. At present, MS represents a major subgroup of myeloid neoplasms and acute leukemia in WHO classification [5].

4. Sites of involvement and symptoms

(54%), followed by ocular region [3, 10, 11].

5. Diagnosis and disease pathology

confirm the malignancy of the mass.

accompanied by pains, bleeding, fever and fatigues [1].

MS can manifest in different anatomical sites. However, there is a lack of study to establish a correlation between AML and predilection for sites by MS. The most commonly involved sites of MS are skin, bone and lymph nodes [3, 10, 11]. In addition, other sites associated with MS include central nervous system (CNS), oral and nasal mucosa, breasts, genitourinary tract, chest wall, testis etc. Skin is the primary sites for the development of MS in pediatric patients

Myeloid Sarcoma: The Other Side of Acute Leukemia http://dx.doi.org/10.5772/intechopen.74931 117

In majority of instances, MS is asymptomatic. Even so, depending on the size and location of the tumor, the most common signs and symptoms associated with MS are compression

At present, there is no specific diagnosis for MS. Given the fact that MS in majority of cases is asymptomatic and does not elicit any specific symptoms, it often poses serious diagnostic challenge for a clinician. Consequently, MS is often misdiagnosed as large cell lymphoma, malignant melanoma, extramedullary hematopoiesis or inflammation. However, diagnosis of MS in association with existing leukemia is comparatively easier than isolated MS. Detection and identification of MS requires the coordinated intervention of different medical procedure. Computed tomography (CT) and magnetic resonance imagery (MRI) are generally used for the detection of the tumors [19]. Following the detection of tumors biopsies are conducted to

However, accurate diagnosis of MS requires histological examination and immunophenotypic analysis. Histological analysis of MS generally elicits myeloid cells at different stages of maturation. The infiltrating leukemic cells generally elicit irregular large nuclei and large cytoplasm-to-nuclear ratio. Depending on the predominant cell types in the tumors, MS are classified into granulocytic, monoblastic and myelomonocytic. In addition, depending on the maturity of the cells, MS are further subdivided into immature, mature and blastic types [11]. In addition to morphology, cytochemical stainings on imprints may allow for confirming the myeloid affiliation and differentiating granulocytic-lineage and monoblastic forms. According to the WHO 2016 classification, cytochemical stains may include myeloperoxidase and naphthol AS-D chloroacetate esterase (positive in granulocytic MS), as well as non-specific esterase (positive in monoblastic MS) [5]. The diagnosis is further validated by immunophenotyping. Flow cytometric analysis on cell suspensions can be performed; however, immunohistochemistry on paraffin-embedded tissue sections is more commonly used for the detection of lineage affiliation and evaluation of maturation. MS are usually positive for myeloid and monocytic markers, i.e. CD33, CD68, lysozyme, the more immature markers such as CD117 and CD34, CD61, glycophorin, CD4, etc. CD99 and TdT may also be positive. CD56 can be detected in
