Terminal deoxynucleotide transferase (TdT)

Immunohistochemical expression

• precursor T and B cells

• multipotent cells of thymus and bone marrow

• T-ALL / T lymphoblastic lymphoma1

• B-ALL / B lymphoblastic lymphoma1

• some AML2

• lymphoblastic transformation in CGL; these cases have a better prognosis than TdT- non-lymphoid blast crises

• not by other non-Hodgkin's lymphoma

• Merkel cell carcinoma

Diagnostic utility

•  Diagnosis of T-ALL / T lymphoblastic lymphoma and B-ALL / B lymphoblastic lymphoma

• Diagnosis of type B thymoma

References

1 Soslow RA, Bhargava V,Warnke RA MIC2, TdT, bcl-2, and CD34 expression in paraffin-embedded high-grade lymphoma/acute lymphoblastic leukemia distinguishes between distinct clinicopathologic entities. Hum Pathol 1997; 28:1158-65

2 Drexler HG, Sperling C,Ludwig WD Terminal deoxynucleotidyl transferase (TdT) expression in acute myeloid leukemia. Leukemia 1993; 7:1142-50

©SMUHT/PW Bishop