Stains & molecular markers
TdT
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: TdT[title]
TdT
Author: Nat Pernick, M.D.
Topic Completed: 1 June 2005
Minor changes: 10 December 2020
Copyright: 2003-2021, PathologyOutlines.com, Inc.
PubMed Search: TdT[title]
Table of Contents
Definition / general | Uses by pathologists | Microscopic (histologic) images | Positive staining - normal | Positive staining - disease | Negative stainingCite this page: Pernick N. TdT. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainstdt.html. Accessed January 22nd, 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
- Interpretation: nuclear stain
- Marker of B or T cell acute lymphoblastic leukemia/lymphoma (only rarely negative, Arch Pathol Lab Med 2000;124:92)
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
- Hematogones (B and T cell precursors, coarsely granular or speckled pattern of TdT immunofluorescence, which often intensely aligns the nuclear membrane, Am J Clin Pathol 2008;129:700), cortical thymocytes
- Note: TdT+ lymphoid precursors are present in benign pediatric lymph nodes (Am J Clin Pathol 2002;118:248) and tonsils (Am J Clin Pathol 2001;116:12), causing possible confusion in ALL patients
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
