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Nonpositive Terminal Deoxynucleotidyl Transferase in Pediatric Precursor B-Lymphoblastic Leukemia

Lanting Liu MD, Loris McGavran PhD, Mark A. Lovell MD, Qi Wei, Bette A. Jamieson, Sara A. Williams, Norma N. Dirks, M. Susan Danielson, Lara M. Dubie, Xiayuan Liang MD
DOI: http://dx.doi.org/10.1309/QD18PPV1NH3TEUTF 810-815 First published online: 1 June 2004

Abstract

Terminal deoxynucleotidyl transferase (TdT) is a unique intranuclear DNA polymerase that catalyzes the template-independent addition of deoxynucleotides to the 3'-hydroxyl terminus of oligonucleotide primers. The expression of TdT is restricted to lymphoid precursors. It is a useful marker in distinguishing acute lymphoblastic leukemia (ALL) from mature lymphoid neoplasms. Although TdT– T-cell ALL has been reported in the literature rarely, the frequency and significance of TdT-nonpositive (TdTnp) B-cell ALL have not been examined extensively. We reviewed the immunophenotypes of 186 new cases of pediatric B-cell ALL and found 5 TdTnp cases (2.7%). They showed significantly higher frequencies of a WBC count of more than 50,000/μL (>50.0 × 109/L), CD10–, CD34–, and MLL gene rearrangement compared with those in TdT+ cases (3/5 [60%] vs 27/181 [14.9%], P = .03; 3/5 [60%] vs 11/181 [6.1%], P = .003; 4/5 [80%] vs 24/179 [13.4%], P = .002; 3/5 [60%] vs 9/181 [5.0%], P = .0019; respectively). These results indicate that nonpositive TdT does not rule out a diagnosis of ALL and suggest that TdTnp B-cell ALL might be associated with CD10– and CD34– disease, a high WBC count, and MLL gene rearrangement.

Key Words:
  • Terminal deoxynucleotidyl transferase
  • Acute lymphoblastic leukemia
  • Immunophenotype
  • MLL