Chicken lymphomas are generally classified into three virus-induced tumors: Marek’s disease (MD), lymphoid leukosis, and reticuloendotheliosis, with MD being the most common T-cell lymphoma in commercial poultry. In this study, we describe 23 cases of a novel cytotoxic T-cell lymphoma affecting layer chickens aged >1 year in Japan that is distinct from previously known chicken lymphomas. These cases were initially misidentified as MD during routine poultry inspection but were later confirmed as a distinct and novel form of lymphoma. The average incidence of this lymphoma was 0.016%. Histological analysis revealed that the tumors comprised small uniformly round cells that were CD3+, CD4−, and CD8+, indicating a cytotoxic T-cell origin. Investigations using immunohistochemistry, in situ hybridization, and polymerase chain reaction ruled out the involvement of known tumor-inducing viruses in the development of these novel lymphomas. These findings confirm the existence of a novel lymphoma type in chickens and provide key histopathological and epidemiological data to aid in definitive diagnosis.
AhmedHMaysJKiupelM, et al. Development of reliable techniques for the differential diagnosis of avian tumour viruses by immunohistochemistry and polymerase chain reaction from formalin-fixed paraffin-embedded tissue sections. Avian Pathol. 2018;47:364–374.
2.
AlaggioRAmadorCAnagnostopoulosI, et al. The 5th edition of the World Health Organization classification of haematolymphoid tumours: lymphoid neoplasms. Leukemia. 2022;36:1720–1748.
3.
AltanerovaVBanJKettmannR, et al. Induction of leukemia in chicken by bovine leukemia virus due to insertional mutagenesis. Arch Geschwulstforsch. 1990;60:89–96.
4.
AlyMMSmithEJFadlyAM.Detection of reticuloendotheliosis virus infection using the polymerase chain reaction. Avian Pathol. 1993;22:543–554.
5.
BiggsPMPayneLN.Studies on Marek’s disease. I. Experimental transmission. J Natl Cancer Inst. 1967;39:267–280.
6.
CrittendenLBWitterRLOkazakiW, et al. Lymphoid neoplasms in chicken flocks free of infection with exogenous avian tumor viruses. J Natl Cancer Inst. 1979;63:191–200.
7.
DoakRLMunnellJFRaglandWL.Ultrastructure of tumor cells in Marek’s disease virus-infected chickens. Am J Vet Res. 1973;34:1063–1069.
8.
FechnerHKurgAGeueL, et al. Evaluation of polymerase chain reaction (PCR) application in diagnosis of bovine leukaemia virus (BLV) infection in naturally infected cattle. Zentralbl Veterinarmed B. 1996;43:621–630.
9.
GimenoIMWitterRLFadlyAM, et al. Novel criteria for the diagnosis of Marek’s disease virus-induced lymphomas. Avian Pathol. 2005;34:332–340.
10.
GimenoIMWitterRLHuntHD, et al. The pp38 gene of Marek’s disease virus (MDV) is necessary for cytolytic infection of B cells and maintenance of the transformed state but not for cytolytic infection of the feather follicle epithelium and horizontal spread of MDV. J Virol. 2005;79:4545–4549.
11.
JonesDLeeLLiuJL, et al. Marek disease virus encodes a basic-leucine zipper gene resembling the fos/jun oncogenes that is highly expressed in lymphoblastoid tumors. Proc Natl Acad Sci USA. 1992;89:4042–4046.
12.
KurokawaAYamamotoY. Immunohistochemical identification of T and B lymphocytes in formalin-fixed paraffin-embedded chicken tissues using commercial antibodies. Vet Immunol Immunopathol. 2020;228:110088.
13.
KurokawaAYamamotoY. Development of monoclonal antibodies specific to Marek disease virus-EcoRI-Q (Meq) for the immunohistochemical diagnosis of Marek disease using formalin-fixed, paraffin-embedded samples. J Vet Diagn Invest. 2022;34:458–464.
14.
KurokawaAYamamotoY.Immunohistochemical diagnosis of Marek’s disease based on Meq detection in 104 field cases of chicken lymphoma. Avian Dis. 2024;68:293–298.
15.
KurokawaAYamamotoY.Immunohistochemical identification of immune cell subsets in formalin- and zinc-fixed, paraffin-embedded tissues from chicken and duck using commercial antibodies. Vet Immunol Immunopathol. 2025;281:110898.
16.
LanHYMuWNikolic-PatersonDJ, et al. A novel, simple, reliable, and sensitive method for multiple immunoenzyme staining: use of microwave oven heating to block antibody crossreactivity and retrieve antigens. J Histochem Cytochem. 1995;43:97–102.
17.
LupianiBLeeLFCuiX, et al. Marek’s disease virus-encoded Meq gene is involved in transformation of lymphocytes but is dispensable for replication. Proc Natl Acad Sci USA. 2004;101:11815–11820.
MurataSChangKSLeeSI, et al. Development of a nested polymerase chain reaction method to detect oncogenic Marek’s disease virus from feather tips. J Vet Diagn Invest. 2007;19:471–478.
PowellPCPayneLNFrazierJA, et al. T lymphoblastoid cell lines from Marek’s disease lymphomas. Nature. 1974;251:79–80.
22.
SantosVLSLWilliamsSMZavalaG, et al. Detection of reticuloendotheliosis virus by immunohistochemistry and in situ hybridization in experimentally infected Japanese quail embryos and archived formalin-fixed and paraffin-embedded tumours. Avian Pathol. 2008;37:451–456.
23.
SchatKAChenCLCalnekBW, et al. Transformation of T-lymphocyte subsets by Marek’s disease herpesvirus. J Virol. 1991;65:1408–1413.
24.
SilvaRFFadlyAMTaylorSP.Development of a polymerase chain reaction to differentiate avian leukosis virus (ALV) subgroups: detection of an ALV contaminant in commercial Marek’s disease vaccines. Avian Dis. 2007;51:663–667.
25.
WitterRLGimenoIMPandiriAR, et al. Tumor Diagnosis Manual: The Differential Diagnosis of Lymphoid and Myeloid Tumors in the Chicken. Jacksonville, FL: American Association of Avian Pathologists;2010.
26.
WitterRLSharmaSMFadlyAM.Nonbursal lymphomas induced by nondefective reticuloendotheliosis virus. Avian Pathol. 1986;15:467–486.
27.
YamamotoHYoshinoTHiharaH, et al. Histopathologic comparison of Marek’s disease with avian lymphoid leukosis. Natl Inst Anim Health Q (Tokyo). 1972;12:29–42.
