en Pediatric Hematology & Oncology Pediatric Hematology & Oncology گزارش مورد Case report <p style="text-align: justify;"><span style="line-height:2;"><span style="font-family:Arial;"><span style="font-size:14px;">Acute lymphoblastic leukemia/lymphomas are tumors made of the precursor B or T cells. Precursor B cell type presents as acute leukemia, and most cases of pediatric leukemia are of this type. Malignancies originated from T cells are less common and are often manifested as lymphoma in adolescents. Terminal deoxynucleotidyl tranferase (TdT) is a DNA polymerase that is present in immature pre-B and pre-T cells. TdT enzyme is a sign of cell immaturity and is used to differentiate the dominant types of lymphoblastic lymphoma from mature lymphoma/leukemia cells. TdT is expressed in 90%&ndash;95% of lymphoblastic lymphoma cells. Childhood TdT negative lymphoblastic leukemia/lymphoma is very infrequent and its prognostic significance remains challenging. It is suggested that TdT negative lymphoblastic leukemia/lymphoma shows poor response to chemotherapy and has a more disastrous course. Here, we report a case of TdT negative T-cell lymphoblastic lymphoma in a 10-year-old boy who presented with respiratory distress.</span></span></span></p> Terminal deoxynucleotidyl tranferase (TdT), Acute lymphoblastic leukemia/lymphomas, TdT negative T cell malignancy, Children 140 143 http://ijbc.ir/browse.php?a_code=A-10-699-1&slc_lang=en&sid=1 Fariba Binesh binesh44@yahoo.com 10031947532846009044 10031947532846009044 No Department of Pathology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Alireza Jenabzadeh emamrezamashhad@gmail.com 10031947532846009045 10031947532846009045 No Hematology and Oncology Research Center, Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran Mohammad Ali Dideban akhond1362@gmail.com 10031947532846009046 10031947532846009046 No Department of Pathology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Najmeh Beheshti mojahedmasudah@gmail.com 10031947532846009047 10031947532846009047 No Department of Pathology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Fatemeh Khaleghi jarya931@gmail.com 10031947532846009048 10031947532846009048 No Department of Radiology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Seyed Hossein Shahcheraghi shahcheraghih@gmail.com 10031947532846009049 10031947532846009049 Yes Infectious Diseases Research Center, Shahid Sadoughi Hospital, Shahid Sadoughi University of Medical Sciences, Yazd, Iran