TdT Negativity and ETP Phenotype in Young Patients with Acute T- Lymphoid Leukemia: A Case Report

Case Report

Ann Hematol Oncol. 2021; 8(4): 1339.

TdT Negativity and ETP Phenotype in Young Patients with Acute T- Lymphoid Leukemia: A Case Report

Cetin D1*, Midik MM1, Karadag FK2, Ozsan N3, Pariltay E4, Akin H4 and Saydam G2

1Department of Internal Medicine, Ege University School of Medicine, Turkey

2Department of Hematology, Ege University School of Medicine, Turkey

3Department of Pathology, Ege University School of Medicine, Turkey

4Department of Medical Genetics, Ege University School of Medicine, Turkey

*Corresponding author: Denis Cetin, Department of Internal Medicine, Ege University School of Medicine, Bornova, Izmir, Turkey

Received: February 26, 2021; Accepted: March 29, 2021; Published: April 05, 2021


TdT is generally positive in patients with T-Acute Lymphoblastic Leukemia/ Lymphoma (T-ALL/LBL) and can often become negative after chemotherapy. TdT negativity at the time of diagnosis is not a common condition and is evaluated in favor of a poor prognosis. Due to its infrequent occurrence, there are not enough clinical studies, and there are often publications on the basis of case and case series. While its incidence increases in young people and children, the possibility of accompanying Early T Precursor (ETP) phenotype also increases. The presence of the ETP phenotype has negative repercussions on prognosis. Here, we will describe the diagnosis and treatment process of a young adult patient with TdT negative T-ALL accompanied by the ETP phenotype.


Acute Lymphoblastic Leukemia (ALL) is a hematopoietic malignancy, which is caused by uncontrolled proliferation of immature B/T lymphoid cells. In the United States of America (USA), the incidence of ALL at all ages is 1.38/100,000 people per year, with an estimated 5930 new cases and 1500 deaths due to ALL [1,2]. ALL is more common in childhood than in adults. It constitutes 75-80 % of childhood acute leukemias [3]. The average age of diagnosis is 15 years old and 55.4% of the patients are under 20 years old [4,5].

According to the immunophenotype classification, ALL originates from B cells (B-ALL) and T cells (T-ALL); 85% and 15% respectively [6,7]. Among ALL, T-ALL is detected in adults at a higher rate compared to childhood, but this rate decreases as the age progresses [8]. The World Health Organization (WHO) defines T-ALL as Terminal Deoxynucleotidyl Transferase (TdT) as well as lymphoblasts where the markers CD1a, CD2, CD3, CD4, CD5, CD7 and CD8 are positive. Cytoplasmic CD3 (cCD3) and CD7 are also often positive. T-ALL can be divided into pro-T, pre-T, cortical T and medullary T according to the stages of intra-thymic differentiation [9,10]. In addition, early T cell precursor (ETP) immunophenotype has been identified according to surface markers (lack of CD1a and CD8 expression, negative or weak CD5 expression, and one or more myeloid or stem cell marker expression) [11]. Although it was reported that TdT is negative in 5-12 % of cases, TdT is usually positive at T-ALL [12-16].

TdT is an intranuclear DNA polymerase that catalyzes the addition of deoxynucleotides to oligonucleotides. TdT is highly expressed in lymphoid precursors where it plays a pivotal role in T-cell receptor and immunoglobulin heavy chain gene rearrangement. Indeed, almost all cortical thymocytes and a small subset of bone marrow B-cells express TdT in their nuclei. TdT is an important marker in distinguishing ALL from reactive conditions or mature lymphoid neoplasms [17].

Herein, we reported the diagnosis process and the management of a patient who has TdT negative T-ALL with ETP immunophenotype.

Case Presentation

A 20-year-old female patient with no known additional diseases applied to our health facility due to painless swelling behind the right ear. There was no weight loss, fever, or night sweats in the system questionnaire. On her physical examination, bilateral posterior auricular, submandibular, jugular, supraclavicular, left axillary, bilateral inguinal lymphadenopathy and hepatosplenomegaly were detected. In laboratory examination, hemoglobin 12 g/L, leukocyte count 8.92x10³/μL, neutrophil count 1.11x10³/μL, lymphocyte count 6.81x10³/μL, platelet count 137x10³/μL, erythrocyte sedimentation rate 44 mm/hour, C-Reactive Protein (CRP) 20.26 mg/L (0-5 mg/L), Lactate Dehydrogenase (LDH) 513 U/L (135-225). Her renal function, liver function, and electrolytes were normal on biochemical laboratory evaluation.

On peripheral blood smear 40% blasts were seen and bone marrow aspiration and biopsy were performed. Bone marrow biopsy showed 90% narrow basophilic cytoplasm blast population. Immuno-histochemical examinations revealed extensive and strong positive with CD3 and CD10, mostly positive with CD34 and negative staining with TdT. It is shown in Figure 1.