Stains & CD markers

Topic Completed: 1 June 2005

Minor changes: 20 August 2021

Copyright: 2003-2021,, Inc.

PubMed Search: TdT[title]

Nat Pernick, M.D.
Page views in 2020: 10,905
Page views in 2021 to date: 9,167
Cite this page: Pernick N. TdT. website. Accessed October 21st, 2021.
Definition / general
  • Terminal deoxynucleotidyl transferase; also called terminal transferase
  • Nuclear DNA polymerase in thymic and small number of bone marrow cortical lymphocytes
  • Catalyzes addition of deoxynucleotides to 3' OH ends of oligonucleotides or polydeoxynucleotides
  • Performs DNA synthesis using only single-stranded DNA as the nucleic acid substrate (Biochim Biophys Acta 2010;1804:1151)
  • Used during immunoglobulin and T cell receptor rearrangement, adds diversity to antibody recognition sites
  • Absent in fetal liver hematopoietic stem cells, which impairs junctional diversity in B cells during the fetal period
Uses by pathologists
Microscopic (histologic) images

Case #126

Pre-B lymphoblastic lymphoma of kidney (left), skin (right)

Images hosted on other servers:

Bone marrow: hematogones with coarsely granular or speckled pattern of terminal deoxynucleotidyl transferase (TdT) immunofluorescence, which often intensely aligns the nuclear membrane (green)

Bone marrow: acute myeloid leukemia (left) and recursor B-lymphoblastic leukemia (right) with a finely granular pattern of terminal deoxynucleotidyl transferase (TdT) immunofluorescence, which is uniformly distributed in the nucleus (green)

Lymphoblastic lymphoma with basal cell carcinoma

Merkel cell carcinoma

Positive staining - normal
Positive staining - disease
  • Acute lymphoblastic lymphoma: 95%, diffuse and strong, finely granular pattern of TdT immunofluorescence uniformly distributed in the nucleus
  • Acute myelogenous leukemia / myeloid sarcoma: variable, often weak and focal
  • Blastic plasmacytoid dendritic cell neoplasm: 60% (Am J Surg Pathol 2010;34:75)
  • Indolent T cell proliferations
  • Merkel cell carcinoma: >50% (Mod Pathol 2007;20:1113, Am J Clin Pathol 2011;135:831)
  • Thymoma-lymphocyte predominant
Negative staining
  • Myeloid cells; mature leukemias/lymphomas including Burkitt, diffuse large B cell, MALT, mantle cell, prolymphocytic leukemia (T cell)
  • Small cell lung carcinoma (usually); sarcomas
Back to top
Image 01 Image 02