LETTER TO EDITOR
Year : 2014 | Volume
: 57 | Issue : 4 | Page : 661--662
Atypical immunophenotype of T-cell Acute Lymphoblastic Leukemia
Abhishek Purohit, Mukul Aggarwal, Hara P Pati, Renu Saxena
Department of Haematology, All India Institute of Medical Sciences, New Delhi, India
Dr. Mukul Aggarwal
Department of Hematology, All India Institute of Medical Sciences, New Delhi
|How to cite this article:|
Purohit A, Aggarwal M, Pati HP, Saxena R. Atypical immunophenotype of T-cell Acute Lymphoblastic Leukemia.Indian J Pathol Microbiol 2014;57:661-662
|How to cite this URL:|
Purohit A, Aggarwal M, Pati HP, Saxena R. Atypical immunophenotype of T-cell Acute Lymphoblastic Leukemia. Indian J Pathol Microbiol [serial online] 2014 [cited 2021 Dec 2 ];57:661-662
Available from: https://www.ijpmonline.org/text.asp?2014/57/4/661/142729
T-lymphoblastic leukemia/lymphoma is a lymphoid neoplasm committed to the T cell lineage. T-cell Acute Lymphoblastic Leukemia (T- ALL) typically present with high leucocyte count, and often a large mediastinal mass or other tissue mass. We are presenting a case of precursor T-cell ALL which has both unusual clinical presentation and immunophenotype.
A 15-year-old male patient resident of Himachal Pradesh, presented to hematology department with 10 day history of generalized weakness, low grade intermittent fever and multiple skin bleed. There was no history of any history of cough, breathing difficulty, sore throat, pain abdomen, loose stools, dysuria, bony pains, night sweats or jaundice. The patient was apparently well prior to the illness and his past medical history was uneventful. Physical examination revealed stable vital parameters along with enlarged axillary lymphnodes (2 cm in diameter), which were non-tender, mobile with normal overlying skin. There was no evidence of pallor, icterus, gum hypertrophy or sternal tenderness. Systemic examination did not reveal any abnormality.
Laboratory investigations revealed hemoglobin 97 gm/L, total leucocyte count 712 10 9 /L and platelet count 15 10 9 /L with 96% blasts on peripheral smear. Biochemical investigation revealed evidence of tumor lysis (Serum Urea 118 mg/dL, serum creatinine 1.5 mg/ dL, serum calcium 9.7 mg/dL, phosphate 5.2 mg/ dL, uric acid 8.7 mg/dL), however, liver function tests and coagulation parameters were within normal limits. Bone marrow examination also revealed blast constituting 94% of all nucleated cells which were negative for myeloperoxidase and non-specific estrase cytochemical stains, however, flowcytometric immunophenotyping did not reveal any population in the blast window on CD45/side scatter plot. Majority of the blasts were CD45 negative and were positive for CD2, CD7, CD5, TdT, CD34 and cytoplasmic CD3, and were negative for CD19, Cd10, CD13, CD33, CD117, CD4, CD8 and CD56, cytoplasmic CD79a, myeloperoxidase, suggesting a diagnosis of T- cell Acute lymphoblastic leukemia.
Patient's treatment was started supportive therapy, however he developed altered sensorium on 3 three of admission with multiple parenchymal intracranial hemorrhages and died.
The presenting symptoms and signs of ALL correlate with the leukemic cell burden and the degree of marrow replacement, leading to cytopenias. The most common symptoms include fever, fatigue and lethargy, bone and joint pain, and a bleeding diathesis. Patients with precursor T-cell ALL often have associated mediastinal mass with or without associated pleural effusions, which may cause respiratory distress and superior vena cava syndrome. In T-cell ALL, a leucocyte count greater than 100 10 9 /L is associated with an increased risk of CNS disease. Patients with extreme hyperleucocytosis (>400 10 9 /L) are at high risk for early complications such as CNS hemorrhage and pulmonary and neurological events due to leucostasis and hyperviscosity.  Serious bleeding is rare and occurs primarily in children with co-morbidities, such as hyperleucocytosis, infection, gastro-intestinal ulceration or intra-cranial aneurysms. Literature review suggest extremely low incidence of hemorrhagic deaths reported in older Nordic, St Jude's, UK and German trials. 
The leucocyte common antigen, or CD45, belong to a family of cell surface glycoproteins with a heavily glycosylated extracellular domain, a transmembrane segment, and a large cytoplasmic domain that contains tyrosine phosphatase activity, is found on all hematopoietic cells except erythrocytes and platelets. T cell ALLs are usually CD45 positive. 
The present case of T cell ALL revealed uncommon immunophenotype by showing CD45 negative blast population. Behm et al. in their study on 249 cases of childhood ALL found that all 55 T-cell cases expressed CD45 and expression of the antigen was more extensive for T-cell ALL than for B-lineage ALL. 
Ratei et al. (1998) evaluated the expression pattern of CD45 in 638 childhood ALL cases including childhood B cell precursor (n = 529) and T cell ALL (n = 109) and observed that only four cases (3.7%) of T ALL did not express CD45.  Ari nakamura et al. (2001) evaluated the clinical implications of CD45 expression in acute childhood lymphoblastic leukemia (ALL) and measured the CD45 expression of blast cells from 133 untreated patients with childhood B-precursor ALL (n = 118) or T-ALL (n = 15). Their results showed that the levels of expression of the CD45 antigen on leukemic lymphoblasts were significantly correlated with the clinical features and prognosis of childhood ALL and showed that high expression levels of CD45 antigen significantly correlated with unfavorable outcome of the high-risk patients with B-precursor ALL, however, all the T-ALL cases were positive for CD45 expression. 
To conclude, the presenting case was associated with unusual clinical and laboratory findings. The present case was unusual as despite being T cell ALL, there was no mediatinal mass or pleural effusion but succumbed very early in the disease course to intracranial hemorrhage. Further, blast population in this case was CD45 negative which is very unusual with T-ALL.
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