title: TdT-positive Infiltrate in Inflamed Pediatric Kidney: A Potential Diagnostic Pitfall.
abstract: We encountered a patient with infantile nephrotic syndrome associated with a dense interstitial inflammatory infiltrate and prominent extramedullary hematopoiesis. Immunohistochemical analysis revealed numerous terminal deoxynucleotidyl transferase (TdT)-positive cells, which may raise concern for lymphoblastic lymphoma. Thus, we further characterized a group of pediatric kidneys with inflammation. TdT-positive nuclei were quantitated, and dual immunostains for TdT/CD79a, TdT/CD3, and TdT/CD43 were performed in a subset of cases; flow cytometry was performed in 1 case. TdT-positive nuclei were present in inflamed pediatric kidneys in 40 of 42 patients. TdT counts (average of 3 maximal high-power fields) ranged from 1 to >200, with a mean of 47. The presence and number of TdT-positive nuclei showed a strong association with younger patient age. Extramedullary hematopoiesis was identified in 11/42 patients, all under the age of 1. The presence of extramedullary hematopoiesis did not correlate with TdT count (P=0.158). Dual immunostaining and flow cytometric analysis in 1 case showed weak expression of B-cell markers and favored normal precursor B cells. Although TdT is a common marker of lymphoblastic lymphoma, we have demonstrated that TdT-positive cells may be part of the inflammatory milieu in infant kidneys. Together with cytologic, architectural, and clinical features, these data can help to avoid misinterpretation of involvement by lymphoblastic lymphoma/leukemia.
authors.affiliation: *Department of Pathology, Oregon Health & Science University, Portland, OR †Department of Pathology, Stanford University Medical Center, Stanford, CA.
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Dunlap
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cascio
authors.forename: Xavier
authors.initials: X
authors.lastname: Stacey
authors.forename: Sarah
authors.initials: S
authors.lastname: Click
authors.forename: Megan L
authors.initials: ML
authors.lastname: Troxell
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000032:analysis; D001706:Biopsy; D017252:CD3 Complex / Q000032:analysis; D051925:CD79 Antigens / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D004253:DNA Nucleotidylexotransferase / Q000032:analysis*; D003937:Diagnosis, Differential; D005434:Flow Cytometry; D006411:Hematopoiesis, Extramedullary; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D007668:Kidney / Q000737:chemistry* / Q000473:pathology / Q000601:surgery; D051917:Leukosialin / Q000032:analysis; D008297:Male; D009392:Nephrectomy; D009393:Nephritis / Q000175:diagnosis / Q000378:metabolism* / Q000601:surgery; D009404:Nephrotic Syndrome / Q000175:diagnosis / Q000378:metabolism* / Q000601:surgery; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000378:metabolism; D011237:Predictive Value of Tests; D055815:Young Adult
chemical_list: D015415:Biomarkers; D017252:CD3 Complex; D051925:CD79 Antigens; C497881:CD79A protein, human; D051917:Leukosialin; C465014:SPN protein, human; D004253:DNA Nucleotidylexotransferase