FREE SHIPPING over $40
OVER 10000 FIVE-STAR REVIEWS
5% OFF ALL SUBSCRIPTIONS
100% HAPPINESS GUARANTEE
Analyze Diet
0
Journal of veterinary internal medicine2026; 40(4); aalag143; doi: 10.1093/jvimsj/aalag143

Central nervous system lymphoma and neurolymphomatosis in equids.

Abstract: Lymphoma affecting the central and peripheral nervous systems in equids is rarely reported. Objective: To describe the clinical presentation, neuroanatomical localization, laboratory and pathologic features, type of lymphoma, and outcome to further current knowledge. Methods: Fourteen equids (13 horses, 1 mule). Methods: Retrospective study. Medical records from a veterinary teaching hospital were reviewed (1993-2025). The inclusion criteria consisted of a definitive diagnosis of lymphoma of the nervous system. Data collected included signalment, neurologic findings, laboratory results, imaging, cerebrospinal fluid (CSF) analysis, immunophenotyping, and necropsy examination. Descriptive statistics were used. Results: Nervous system lymphoma, either primary or concurrent with multicentric lymphoma, accounted for 11.6% of lymphoma cases. Multifocal neurologic disease was the most common presentation. Common hematologic findings included leukocytosis with neutrophilia, normal plasma fibrinogen concentration, high neutrophil-to-lymphocyte and red cell distribution width-to-platelet ratios, and hypocalcemia. Cytology of the CSF provided a definitive diagnosis in 56% of sampled cases. Prognosis was poor with a median survival time of 4.5 days from diagnosis. All lymphomas were of B-cell origin, including diffuse large B-cell lymphoma, small lymphocytic lymphoma, and T-cell-rich large B-cell lymphoma. Conclusions: Nervous system lymphoma in equids might be more common than previously reported. Primary nervous system small lymphocytic B-cell lymphoma in a horse and multifocal nervous system lymphoma in a mule have not been reported previously. Analysis of CSF is useful in the antemortem diagnosis of central nervous system lymphoma. Neurologic examination, CSF analysis, and necropsy should be routinely performed in cases of multicentric lymphoma to rule out neurologic involvement.
© The Author(s) 2026. Published by Oxford University Press on behalf of the American College of Veterinary Internal Medicine.
Get Full Text
Publication Date: 2026-07-29 PubMed ID: 42525884PubMed Central: PMC13419072DOI: 10.1093/jvimsj/aalag143Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
LinkedInCopy
  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated lymphoma cases affecting the central and peripheral nervous systems in horses and a mule, characterizing their clinical presentation, diagnostic features, lymphoma types, and patient outcomes.
  • The researchers found that nervous system lymphoma may be more common than previously thought and highlighted the usefulness of cerebrospinal fluid analysis in diagnosis, while noting a generally poor prognosis.

Background and Objective

  • Lymphoma, a type of cancer affecting lymphatic tissue, is known to occur in equids (horses and related species), but involvement of the nervous system (central and peripheral) is rarely documented.
  • The study aimed to expand understanding by describing the clinical signs, neuroanatomical sites involved, laboratory and pathological features, lymphoma types, and outcomes in equids diagnosed with nervous system lymphoma.

Methods

  • A retrospective review of medical records from a veterinary teaching hospital spanning more than 30 years (1993-2025) was conducted.
  • Fourteen equids (13 horses and 1 mule) with confirmed lymphoma affecting the nervous system were included.
  • Data collected involved:
    • Signalment (age, breed, sex)
    • Neurologic clinical findings and localization
    • Laboratory findings (hematology, blood chemistry)
    • Imaging studies when available
    • Cerebrospinal fluid (CSF) analysis
    • Immunophenotyping to classify lymphoma types based on cell origin
    • Necropsy findings after death
  • Descriptive statistics summarized the data.

Key Findings

  • Nervous system lymphoma cases (either primary to the nervous system or concurrent with multicentric lymphoma) accounted for approximately 11.6% of all lymphoma cases in the review period, suggesting it is not as rare as previously believed.
  • Most equids presented with multifocal neurologic deficits, indicating lymphoma affected multiple nervous system regions.
  • Common bloodwork abnormalities included:
    • Leukocytosis (increased white blood cells), especially neutrophilia (high neutrophil count)
    • Normal plasma fibrinogen concentration (an inflammatory marker)
    • Elevated neutrophil-to-lymphocyte ratio (increased proportion of neutrophils relative to lymphocytes)
    • Elevated red cell distribution width-to-platelet ratio
    • Hypocalcemia (low calcium levels)
  • CSF cytology was valuable, providing a definitive lymphoma diagnosis in 56% of cases sampled, demonstrating its diagnostic utility.
  • All lymphomas were of B-cell origin, with subtypes including:
    • Diffuse large B-cell lymphoma
    • Small lymphocytic lymphoma
    • T-cell-rich large B-cell lymphoma
  • Notably, the study reported a primary nervous system small lymphocytic B-cell lymphoma case in a horse and a multifocal nervous system lymphoma case in a mule, both novel findings.
  • Prognosis was poor, with a median survival of only 4.5 days after diagnosis.

Conclusions and Clinical Implications

  • Nervous system lymphoma may be under-recognized in equids, warranting increased clinical awareness.
  • Neurologic examination combined with CSF analysis is important for antemortem diagnosis of central nervous system lymphoma.
  • Routine neurologic assessment, CSF evaluation, and necropsy are recommended in cases of multicentric lymphoma to detect possible nervous system involvement.
  • This study broadens the spectrum of recognized lymphoma types and presentations in equids, including newly reported forms.
  • The overall poor outcome highlights the need for further research into therapeutic strategies and earlier detection methods.

Cite This Article

APA
Aleman M, Calero MI, Woolard KD, O'Connell K, Berryhill E, Vernau W. (2026). Central nervous system lymphoma and neurolymphomatosis in equids. J Vet Intern Med, 40(4), aalag143. https://doi.org/10.1093/jvimsj/aalag143

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: England
Language: English
Volume: 40
Issue: 4
PII: aalag143

Researcher Affiliations

Aleman, Monica
  • Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
Calero, Maria I
  • The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
Woolard, Kevin D
  • Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
O'Connell, Kelly
  • Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
Berryhill, Emily
  • Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.
Vernau, William
  • Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California Davis, Davis, CA, United States.

MeSH Terms

  • Animals
  • Lymphoma / veterinary
  • Lymphoma / pathology
  • Lymphoma / diagnosis
  • Horse Diseases / pathology
  • Horse Diseases / diagnosis
  • Horses
  • Male
  • Female
  • Retrospective Studies
  • Central Nervous System Neoplasms / veterinary
  • Central Nervous System Neoplasms / pathology
  • Central Nervous System Neoplasms / diagnosis
  • Neurolymphomatosis / veterinary
  • Neurolymphomatosis / pathology
  • Neurolymphomatosis / diagnosis
  • Equidae

Grant Funding

  • #V435AM2 / Equine and Comparative Neurology Research Group

Conflict of Interest Statement

The authors declare no conflicts of interest.

References

This article includes 54 references
  1. Jaffe ES. Diagnosis and classification of lymphoma: impact of technical advances.. Semin Hematol 2019;56:30-36.
    doi: 10.1053/j.seminhematol.2018.05.007pmc: PMC7394061pubmed: 30573042google scholar: lookup
  2. Samuels A, Burns TA. Lymphoma & myeloproliferative disease.. Vet Clin North Am Equine Pract 2024;40:441-454.
    doi: 10.1016/j.cveq.2024.07.009pubmed: 39266412google scholar: lookup
  3. Durham AC, Pillitteri CA, San Myint M. Two hundred three cases of equine lymphoma classified according to the World Health Organization (WHO) classification criteria.. Vet Pathol 2013;50:86-93.
    doi: 10.1177/0300985812451603pubmed: 22700849google scholar: lookup
  4. de Leval L, Jaffe ES. Lymphoma classification.. Cancer J 2020;26:176-185.
    doi: 10.1097/PPO.0000000000000451pubmed: 32496451google scholar: lookup
  5. Knowles EJ, Tremaine WH, Pearson GR, Mair TS. A database survey of equine tumours in the United Kingdom.. Equine Vet J 2016;48:280-284.
    doi: 10.1111/evj.12421pubmed: 25594351google scholar: lookup
  6. Wensley FM, Berryhill EH, Magdesian KG. Association of globulin concentrations with prognosis in horses with lymphoma.. Front Vet Sci 2022;9:1086010.
    doi: 10.3389/fvets.2022.1086010pmc: PMC9868912pubmed: 36699338google scholar: lookup
  7. Taintor J, Schleis S. Equine lymphoma.. Equine Vet Educ 2011;23:205-213.
    doi: 10.1111/j.2042-3292.2010.00200.xgoogle scholar: lookup
  8. Morris JM, Lassaline ME, Nunnery CM. Clinical and morphological features of corneal lymphoma in 26 horses (27 eyes).. Equine Vet J 2024;57:1028-1034.
    doi: 10.1111/evj.14446pubmed: 39604144google scholar: lookup
  9. Montgomery JB, Duckett WM, Bourque AC. Pelvic lymphoma as a cause of urethral compression in a mare.. Can Vet J 2009;50:751-754.
    pmc: PMC2696708pubmed: 19794872
  10. Torrent A, Kilcoyne I, Johnson A, Affolter VK, Berryhill E, Aleman M. An atypical presentation of multi-systemic B-cell lymphoma in a horse.. Can Vet J 2019;60:300-304.
    pmc: PMC6380265pubmed: 30872854
  11. Taylor SD, Pusterla N, Vaughan B, Whitcomb MB, Wilson WD. Intestinal neoplasia in horses.. J Vet Intern Med 2006;20:1429-1436.
    doi: 10.1111/j.1939-1676.2006.tb00762.xpubmed: 17186861google scholar: lookup
  12. Taylor SD, Haldorson GJ, Vaughan B, Pusterla N. Gastric neoplasia in horses.. J Vet Intern Med 2009;23:1097-1102.
    doi: 10.1111/j.1939-1676.2009.0356.xpubmed: 19656283google scholar: lookup
  13. Sisó S, Marco-Salazar P, Moore PF. Canine nervous system lymphoma subtypes display characteristic neuroanatomical patterns.. Vet Pathol 2017;54:53-60.
    doi: 10.1177/0300985816658101pubmed: 27511313google scholar: lookup
  14. Fonti N, Parisi F, Aytaş Ç, Degl’Innocenti S, Cantile C. Neuropathology of central and peripheral nervous system lymphoma in dogs and cats: a study of 92 cases and review of the literature.. Animals (Basel) 2023;13:13.
    doi: 10.3390/ani13050862pmc: PMC10000237pubmed: 36899719google scholar: lookup
  15. Kaulen LD, Hielscher T, Doubrovinskaia S. Clinical presentation, management, and outcome in neurolymphomatosis: a systematic review.. Neurology 2024;103:e209698.
    doi: 10.1212/WNL.0000000000209698pubmed: 39102613google scholar: lookup
  16. Palić J, Heier A, Lehmbecker A, Baumgärtner W, Turba ME. A challenging case of lymphoproliferative disease in a cat.. Vet Clin Pathol 2022;51:263-268.
    doi: 10.1111/vcp.13062pubmed: 35181934google scholar: lookup
  17. Morrison LR, Freel K, Henderson I, Hahn C, Smith SH. Lymphoproliferative disease with features of lymphoma in the central nervous system of a horse.. J Comp Pathol 2008;139:256-261.
    doi: 10.1016/j.jcpa.2008.07.008pubmed: 18823902google scholar: lookup
  18. Kannegieter NJ, Alley MR. Ataxia due to lymphosarcoma in a young horse.. Aust Vet J 1987;64:377-379.
    doi: 10.1111/j.1751-0813.1987.tb09608.xpubmed: 3452305google scholar: lookup
  19. Rousseaux CG, Doige CE, Tuddenham TJ. Epidural lymphosarcoma with myelomalacia in a seven-year-old Arabian gelding.. Can Vet J 1989;30:751-753.
    pmc: PMC1681191pubmed: 17423424
  20. Rissi DR, Avery AC, Burnett RC. T-cell-rich, large B-cell lymphoma in the brain of a horse.. J Vet Diagn Invest 2023;35:327-331.
    doi: 10.1177/10406387231164368pmc: PMC10185986pubmed: 36946511google scholar: lookup
  21. Shamis LD, Everitt JI, Baker GJ. Lymphosarcoma as the cause of ataxia in a horse.. J Am Vet Med Assoc 1984;184:1517-1518.
    doi: 10.2460/javma.1984.184.12.1517pubmed: 6547423google scholar: lookup
  22. Zeman DH, Snider TG 3rd, McClure JJ. Vertebral lymphosarcoma as the cause of hind limb paresis in a horse.. J Vet Diagn Invest 1989;1:187-188.
    doi: 10.1177/104063878900100222pubmed: 2488341google scholar: lookup
  23. Lehmbecker A, Liebing J, Barthel Y. Neurolymphomatosis in three horses with multicentric T-cell-rich B-cell lymphoma.. J Comp Pathol 2014;151:181-185.
    doi: 10.1016/j.jcpa.2014.04.004pubmed: 24915887google scholar: lookup
  24. Barton CK, Hughes KL, Cowan C, Nout-Lomas YS, Nelson BB. An unusual cause of femoral nerve paresis in a horse: disseminated B cell lymphoma with plasmacytoid differentiation and direct neuronal invasion.. J Equine Vet Sci 2023;126:104502.
    doi: 10.1016/j.jevs.2023.104502pubmed: 37120116google scholar: lookup
  25. Graham AE, Ricci E, Rocchigiani G, Carslake HB. Diffuse, subcutaneous presentation of neurolymphomatosis in a horse with multicentric lymphoma.. Equine Vet Educ 2024;36:620.
    doi: 10.1111/eve.14013google scholar: lookup
  26. Barba M, Groover ES, Bailey J, Cole R, Christopherson P, Cattley R. Nonclassified lymphoma as a cause of radial nerve paralysis in a horse.. J Equine Vet Sci 2021;98:103371.
    doi: 10.1016/j.jevs.2021.103371pubmed: 33663719google scholar: lookup
  27. Lunn DP, Mayhew IG. The neurological evaluation of horses.. Equine Vet Educ 1989;1:94-101.
    doi: 10.1111/j.2042-3292.1989.tb01355.xgoogle scholar: lookup
  28. Elbeyli A, Kurtul BE, Ozcan DO, Ozcan SC, Dogan E. Assessment of red cell distribution width, platelet/lymphocyte ratio, systemic immune-inflammation index, and neutrophil/lymphocyte ratio values in patients with central retinal artery occlusion.. Ocul Immunol Inflamm 2022;30:1940-1944.
    doi: 10.1080/09273948.2021.1976219pubmed: 34524949google scholar: lookup
  29. Jiang M, Shen J, Muhammad B, Geng D. Red blood cell distribution width to platelet ratio predicts early neurological deterioration in acute ischemic stroke patients receiving intravenous thrombolysis.. J Stroke Cerebrovasc Dis 2023;32:107146.
    doi: 10.1016/j.jstrokecerebrovasdis.2023.107146pubmed: 37148627google scholar: lookup
  30. Johnson MM, Gicking JC, Keys DA. Evaluation of red blood cell distribution width, neutrophil-to-lymphocyte ratio, and other hematologic parameters in canine acute pancreatitis.. J Vet Emerg Crit Care (San Antonio) 2023;33:587-597.
    doi: 10.1111/vec.13325pubmed: 37573255google scholar: lookup
  31. Scalco R, de Oliveira GN, da Rosa CB. Red blood cell distribution width to platelet ratio in neonatal foals with sepsis. J Vet Intern Med 2023;37:1552-1560.
    doi: 10.1111/jvim.16793pmc: PMC10365058pubmed: 37306395google scholar: lookup
  32. Chen B, Ye B, Zhang J, Ying L, Chen Y. RDW to platelet ratio: a novel noninvasive index for predicting hepatic fibrosis and cirrhosis in chronic hepatitis B. PLoS One 2013;8:e68780.
    doi: 10.1371/journal.pone.0068780pmc: PMC3714293pubmed: 23874760google scholar: lookup
  33. Alaggio R, Amador C, Anagnostopoulos I. The 5th edition of the World Health Organization classification of haematolymphoid tumours: lymphoid neoplasms. Leukemia 2022;36:1720-1748.
    doi: 10.1038/s41375-022-01620-2pmc: PMC9214472pubmed: 35732829google scholar: lookup
  34. Meichner K, Kraszeski BH, Durrant JR. Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B-cell lymphoma. Vet Clin Pathol 2017;46:64-71.
    doi: 10.1111/vcp.12435pubmed: 28001311google scholar: lookup
  35. Kondratjeva J, Julien F, Coutelier C. Cutaneous epitheliotropic T-cell lymphoma in a donkey—a case report. BMC Vet Res 2022;18:267.
    doi: 10.1186/s12917-022-03365-7pmc: PMC9275177pubmed: 35821128google scholar: lookup
  36. Keller SM, Vernau W, Moore PF. Clonality testing in veterinary medicine: a review with diagnostic guidelines. Vet Pathol 2016;53:711-725.
    doi: 10.1177/0300985815626576pubmed: 26933096google scholar: lookup
  37. Baker JR, Ellis CE. A survey of post mortem findings in 480 horses 1958 to 1980: (1) causes of death. Equine Vet J 1981;13:43-46.
    doi: 10.1111/j.2042-3306.1981.tb03448.xpubmed: 7238480google scholar: lookup
  38. Lester GD, MacKay RJ, Smith-Meyer B. Primary meningeal lymphoma in a horse. J Am Vet Med Assoc 1992;201:1219-1221.
    doi: 10.2460/javma.1992.201.08.1219pubmed: 1429163google scholar: lookup
  39. Sano Y, Okamoto M, Ootsuka Y. Blindness associated with nasal/paranasal lymphoma in a stallion. J Vet Med Sci 2017;79:579-583.
    doi: 10.1292/jvms.16-0537pmc: PMC5383180pubmed: 28163275google scholar: lookup
  40. Westerman TL, Poulsen KP, Schlipf JW Jr. Neurotropic T-cell-rich B-cell lymphoma in a 14-year-old Morgan gelding. Can Vet J 2014;55:379-382.
    pmc: PMC3953942pubmed: 24688140
  41. Bearth ND, Donati B, Beckmann K. Femoral B-cell neurolymphomatosis in a horse with multicentric lymphoma. Equine Vet Educ 2022;35:650-656.
    doi: 10.1111/eve.13846google scholar: lookup
  42. Paraschou G, Xue C, Egan R, Bolfa P. Multicentric lymphoma in a donkey with intestinal and bone marrow involvement. BMC Vet Res 2024;20:57.
    doi: 10.1186/s12917-024-03903-5pmc: PMC10868081pubmed: 38360691google scholar: lookup
  43. du Toit N, Genovese LM, Dalziel RG, Smith SH. Pulmonary angiocentric lymphoma (lymphomatoid granulomatosis) in a donkey. J Comp Pathol 2012;146:24-29.
    doi: 10.1016/j.jcpa.2011.03.008pubmed: 21571299google scholar: lookup
  44. Madron MS, Caston SS, Reinertson EL, Tracey AK, Hostetter JM. Diagnosis and treatment of a primary splenic lymphoma in a mule. Equine Vet Educ 2011;23:606-611.
    doi: 10.1111/j.2042-3292.2011.00250.xgoogle scholar: lookup
  45. Norman TE, Rodrigues A, Russell KE. B cell lymphoma and secondary leukaemia in a mule. Equine Vet Educ 2012;24:599-603.
    doi: 10.1111/j.2042-3292.2011.00335.xgoogle scholar: lookup
  46. de Souza GG, Lacerda ZA, de Moura FBC. Enteric associated T-cell lymphoma in a mule. J Equine Vet Sci 2024;135:105050.
    doi: 10.1016/j.jevs.2024.105050pubmed: 38527562google scholar: lookup
  47. Davis CR, Valentine BA, Gordon E. Neoplasia in 125 donkeys (): literature review and a survey of five veterinary schools in the United States and Canada. J Vet Diagn Invest 2016;28:662-670.
    doi: 10.1177/1040638716665659pubmed: 27698162google scholar: lookup
  48. Morrow LD, Smith KC, Piercy RJ. Retrospective analysis of post-mortem findings in 1,444 aged donkeys. J Comp Pathol 2011;144:145-156.
    doi: 10.1016/j.jcpa.2010.08.005pubmed: 20880543google scholar: lookup
  49. Meyer J, Delay J, Bienzle D. Clinical, laboratory, and histopathologic features of equine lymphoma. Vet Pathol 2006;43:914-924.
    doi: 10.1354/vp.43-6-914pubmed: 17099148google scholar: lookup
  50. İlhan M, İlhan G, Gök AF, Bademler S, Verit Atmaca F, Ertekin C. Evaluation of neutrophil-lymphocyte ratio, platelet-lymphocyte ratio and red blood cell distribution width-platelet ratio as early predictor of acute pancreatitis in pregnancy. J Matern Fetal Neonatal Med 2016;29:1476-1480.
    doi: 10.3109/14767058.2015.1051026pubmed: 26043647google scholar: lookup
  51. Pfeifer ME, Prittie JE, Zollo AM, Weltman JG. Red cell distribution width, illness severity, and all-cause mortality in dogs admitted to the ICU. J Vet Emerg Crit Care (San Antonio) 2022;32:168-172.
    doi: 10.1111/vec.13146pubmed: 34967099google scholar: lookup
  52. Bento L, Díaz-López A, Barranco G. New prognosis score including absolute lymphocyte/monocyte ratio, red blood cell distribution width and beta-2 microglobulin in patients with diffuse large B-cell lymphoma treated with R-CHOP: Spanish lymphoma group experience (GELTAMO). Br J Haematol 2020;188:888-897.
    doi: 10.1111/bjh.16263pubmed: 31782146google scholar: lookup
  53. Scott BJ, Douglas VC, Tihan T, Rubenstein JL, Josephson SA. A systematic approach to the diagnosis of suspected central nervous system lymphoma. JAMA Neurol 2013;70:311-319.
    doi: 10.1001/jamaneurol.2013.606pmc: PMC4135394pubmed: 23319132google scholar: lookup
  54. Cian F, Tyner G, Martini V, Comazzi S, Archer J. Leukemic small cell lymphoma or chronic lymphocytic leukemia in a horse. Vet Clin Pathol 2013;42:301-306.
    doi: 10.1111/vcp.12057pubmed: 23909896google scholar: lookup

Citations

This article has been cited 0 times.
Subscribe to our newsletter
Join 106,387 horse owners like you who receive our email updates on horse health and nutrition.