Diagnostically misleading aberrant terminal deoxynucleotidyl transferase expression in germ cell tumors

Pol J Pathol. 2022;73(2):159-165. doi: 10.5114/pjp.2022.120098.


Terminal deoxynucleotidyl transferase (TdT) is a unique type of DNA polymerase predominantly expressed in precursor lymphoid cells and acute lymphoblastic leukemia. It participates in the junctional diversity of T-cell receptors and immunoglobulins. Recently, aberrant TdT expression was found in seminomas. Here, we evaluated the expression of TdT in our cohort of germ cell tumors (GCTs) with two anti-TdT antibody clones. We included 173 cases of testicular GCTs, 5 ovarian dysgerminomas, and one gonadoblastoma in the study. Tissue microarrays containing representative tumor samples were constructed and subsequently stained with anti-TdT monoclonal rabbit antibody EP266 (Dako) and TdT rabbit polyclonal antibody (Cell Marque). Expression was assessed with the H-score. No specific nuclear reaction was observed for the polyclonal anti-TdT antibody. The H-score values varied between the histological subtypes for the EP266 antibody. Positive nuclear staining was consistently seen in germ cell neoplasia in situ , seminoma, dysgerminoma, and embryonal carcinoma. Pure tumors had higher TdT H-scores than the mixed ones. Teratomas, yolk sac tumors, and choriocarcinomas were almost uniformly negative. Our study confirms that aberrant expression of TdT by testicular and ovarian GCTs exemplifies a potential diagnostic pitfall in histopathological diagnostics.

Keywords: embryonal carcinoma; germ cell tumor; immunohistochemistry; pathology; seminoma; testis; terminal deoxynucleotidyl transferase.

MeSH terms

  • Animals
  • Biomarkers, Tumor
  • DNA Nucleotidylexotransferase
  • DNA-Directed DNA Polymerase
  • Dysgerminoma*
  • Female
  • Humans
  • Immunohistochemistry
  • Male
  • Neoplasms, Germ Cell and Embryonal*
  • Ovarian Neoplasms* / pathology
  • Rabbits
  • Testicular Neoplasms* / diagnosis


  • DNA Nucleotidylexotransferase
  • Biomarkers, Tumor
  • DNA-Directed DNA Polymerase