title: Detection of terminal deoxynucleotidyl transferase (TdT) in nonhematopoietic small round cell tumors of children.
abstract: In the differential diagnosis of small round cell tumors (SRCTs), terminal deoxynucleotidyl transferase (TdT) is often used as a marker for lymphoblastic lymphomas and leukemias. However, the specificity of TdT using the avidin-biotin-immunoperoxidase (ABC) method is not well documented. To address this issue, we stained paraffin-embedded biopsy specimens of 64 cases of childhood SRCTs using the ABC method with anti-TdT. For any TdT-positive tumors, an additional antibody panel for lymphoid markers was applied. Two patterns of TdT positivity were observed: (1) tumor specific, consisting of strong to moderate nuclear staining, and (2) scattered positive lymphoid cells, usually in a perivascular location and expressing T-cell markers. Analysis showed that 7 of 10 medulloblastomas stained with TdT in a tumor-specific pattern (4 cases moderately to strongly positive in 75-100% of tumor cells, 3 cases weakly to moderately positive in 25-50% of cells). Also, 1 of 19 rhabdomyosarcomas and 1 of 8 Ewing's sarcomas showed moderate to strong tumor-specific TdT staining in 100 and 10% of cells, respectively. Scattered TdT-positive lymphoid cells were observed in 27% of these 64 SRCTs. These findings emphasize that TdT positivity should not be relied upon exclusively for making a diagnosis of lymphoblastic leukemia or lymphoma or ruling out other SRCTs.
authors.affiliation: Department of Pathology, University of Utah Health Sciences Center, Salt Lake City 84134, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Mathewson
authors.forename: C R
authors.initials: CR
authors.lastname: Kjeldsberg
authors.forename: S L
authors.initials: SL
authors.lastname: Perkins
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D004253:DNA Nucleotidylexotransferase / Q000032:analysis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D009369:Neoplasms / Q000737:chemistry* / Q000175:diagnosis / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D004253:DNA Nucleotidylexotransferase