Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 10 1 2016 04 08 13 20 EN Shano Naseem Assistant Professor, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Maninderbir Kaur Senior Resident, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Man Sachdeva Assistant Professor, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Jasmina Ahluwalia Associate Professor, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Reena Das Professor, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Neelam Varma Professor and Head, Department of Hematology, Postgraduate Institute of Medical Education and Research, Chandigarh Subhash Varma Professor and Head, Department of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh 2015 10 15 2015 10 17 Background: Mature T/ NK-cell neoplasms are a rare group of disorders and their presentation as leukemia is even rarer. Most of the previous studies have focused on mature B-cell lineage leukemias and there is a paucity of data on mature T/NK-cell lineage leukemias. We, therefore, planned this study to analyze their spectrum, frequency, morphology and immunophenotypic features. Methods: All cases of lymphomas presenting as leukemia over a period of two and a half years were evaluated. Detailed analysis of cases with T/NK-cell lineage was done for their clinical, hematological and immunophenotypic features. Results: A total of 262 cases of mature lymphoid neoplasms presented as leukemia during the study period. Of whom, only 8 (3.1%) cases were of T /NK-cell lineage and the remaining (96.9%) were of B-cell lineage. Of 8 cases, 4 (50%) had T-prolymphocytic leukemia, 2 (25%) had chronic lymphoproliferative disorder- natural killer cell and 1 (12.5%) case of each T-large granular lymphocytic leukemia and hepatosplenic γ/δ T-NHL. Conclusion: T/NK-cell leukemias are rare. Along with clinical and morphological features, pattern of immunophenotypic markers is vital for their diagnosis and subcategorization. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/470 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/470/470