Myeloid Sarcoma: Evaluation of Histopathology, Immunoprofile and Cytogenetics

Abstract

Introduction: Myeloid Sarcoma (MS), an uncommon tumour of immature myeloid blasts at extramedullary sites can be diagnostically challenging, if it is present de novo, precedes Acute Myeloid Leukaemia (AML) or Myeloproliferative Neoplasm (MPN). There are a few studies in literature with a substantial number of cases on clinicopathological, Immunophenotypic (IPT) and Immunohistochemical (IHC) characteristics of MS. Aim: This study was aimed to analyse myeloid sarcoma in Indian population according to the age, gender, site of involvement, differential diagnoses, IHC, IPT and cytogenetics and to add some to the existing knowledge. Materials and Methods: The present cross-sectional study was conducted at Gujarat Cancer Research Institute, Ahmedabad, with a total of 38 patients, diagnosed over past three years (January 2017 to December 2019). Clinical, morphological, IHC, IPT and molecular data of those 38 patients were retrieved and analysed. Results: Out of 38 cases, 16 (42.1%) and 13 (34.2%) cases were previously diagnosed cases of AML and Chronic Myeloid Leukaemia (CML) respectively. Nine patients (23.7%) presented as de novo. Most common site was lymph node (12/38, 31%), followed by breast, vertebra and other unusual sites. Myeloperoxidase (MPO) (31/38, 81.5%), CD117(25/35, 71.4%), CD45 (21/23, 91.3%), CD43 (14/22, 63.6%), CD68 (12/28, 42.8%), CD34 (15/37, 40.5%), CD33 (14/14, 100%), CD13 (15/16, 93.7%), HLA-DR (11/12, 91.6%), CD99 (3/29, 10.3%) and Terminal deoxynucleotidyl Transferase (TdT) (1/9, 11.1%) were expressed by tumour cells. However, epithelial mesenchymal, B and T lymphoid markers were negative. The present study found inv(16) and t(8;21) in MS in known AML patients. Among the known CML patients, two had variant positive for t (9;22) {t (2;9;22) (p23;q34;q11.2)}. Conclusion: Results of present study depicts that considering MS in differential diagnosis in its de novo presentation is necessary to prevent wrong diagnosis and help early treatment of these patients.