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Home / Equine Research Bank / J Vet Diagn Invest / Cancer of unknown primary in a mare: case report and compara...
Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc2021; 33(6); 1142-1146; doi: 10.1177/10406387211030509

Cancer of unknown primary in a mare: case report and comparative pathology review.

Abstract: A 25-y-old Percheron mare was admitted to the teaching hospital because of lethargy and intractable dyspnea. Thoracoabdominal ultrasound examination identified severe peritoneal effusion, mild bilateral pleural effusion, and a diffuse pulmonary nodular pattern. Cytology of peritoneal fluid revealed a hypercellular sample with clusters of neoplastic polygonal cells and admixed macrophages. Euthanasia was followed by postmortem examination; marked bi-cavitary effusion was present, and innumerable up to 4-cm diameter, round-to-floriform nodules were diffusely evident throughout serosal surfaces as well as the pulmonary and hepatic parenchyma. Disseminated adenocarcinoma, predominantly affecting lung and liver with widespread serosal implantation, was confirmed on light microscopy. Neoplastic cells had strong immunolabeling for pancytokeratin and lacked immunoreactivity to vimentin, napsin A, and Pax8. Cytokeratin 7 and thyroid transcription factor-1 were non-contributory given absent and inconsistent internal control reactivity, respectively. Such results, combined with the lack of a major mass that would indicate a primary site, were supportive of carcinoma of unknown primary site, which remains a conundrum in human oncology, and is poorly explored in veterinary medicine, mainly as a result of clinical and diagnostic limitations.
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Publication Date: 2021-07-11 PubMed ID: 34250853PubMed Central: PMC8546480DOI: 10.1177/10406387211030509Google Scholar: Lookup
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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.

The research article discusses a case of a horse with advanced cancer whose primary location was unknown. This is the first case of carcinoma of unknown primary site in a horse, showcasing the challenges in diagnosing and treating such conditions in veterinary medicine.

Case Overview

  • The case discussed involves a 25-year-old Percheron mare. The horse was admitted to a teaching hospital despite presenting with symptoms of lethargy and intractable dyspnea, which indicates severe difficulty breathing.
  • Upon examination using a thoracoabdominal ultrasound, it was found that the horse had severe peritoneal effusion (accumulation of fluid in the peritoneal cavity), mild bilateral pleural effusion (accumulation of fluid around the lungs), and a diffuse pulmonary nodular pattern (spread of nodules across the lungs).
  • The cytology of the peritoneal fluid revealed a hypercellular sample, indicating an abnormal increase in cell count. This sample was populated with clusters of neoplastic polygonal cells (indicating the presence of tumors) and admixed macrophages (immune cells that phagocytose or consume foreign substances).

Post Mortem Examination and Findings

  • After euthanasia, a postmortem examination was conducted where it was noted that there was a marked bi-cavitary effusion, suggestive of a serious health issue. There was also the presence of numerous nodules of up to 4 cm in diameter diffused throughout the serosal surfaces and the pulmonary and hepatic parenchyma (functional tissue in the lung and liver).
  • On examination with light microscopy, it was determined that the nodules were a form of disseminated, or widely spread, adenocarcinoma, a type of cancer that focuses primarily on the glandular cells of the body. This adenocarcinoma was predominantly affecting the lung and liver. But there was also widespread implantation on the serosal surfaces, the thin membrane lining the internal cavities of the body.

Immunolabeling and Diagnostics

  • The neoplastic cells were tested for various immunoreactive markers. They came out strongly positive for pancytokeratin, an epithelial marker. But, they showed no reactivity to vimentin (a protein indicating mesenchymal cells), napsin A (a protein suggestive of lung adenocarcinoma), and Pax8 (a transcription factor often used in the diagnosis of renal, ovarian, and thyroid cancers).
  • Cytokeratin 7 and thyroid transcription factor-1 tests were non-contributory as they lacked internal control reactivity, which means these tests bore no significant impact on the diagnosis.
  • Because of the findings, along with the lack of a mass that would point towards a primary site of the cancer, it was concluded that the mare had carcinoma of unknown primary site. This kind of carcinoma poses distinct challenges in human oncology due to its diagnostic difficulty. It is barely explored in veterinary medicine given the clinical and diagnostic limitations.

Cite This Article

APA
Brinker EJ, Ceriotti S, Naskou MC, Spangler EA, Groover ES, Neto RLALT. (2021). Cancer of unknown primary in a mare: case report and comparative pathology review. J Vet Diagn Invest, 33(6), 1142-1146. https://doi.org/10.1177/10406387211030509

Publication

Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
ISSN: 1943-4936
NlmUniqueID: 9011490
Country: United States
Language: English
Volume: 33
Issue: 6
Pages: 1142-1146

Researcher Affiliations

Brinker, Emily J
  • Departments of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Ceriotti, Serena
  • Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Naskou, Maria C
  • Departments of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Spangler, Elizabeth A
  • Departments of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Groover, Erin S
  • Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Neto, Rachel L A L T
  • Departments of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.

MeSH Terms

  • Adenocarcinoma / veterinary
  • Animals
  • Carcinoma / veterinary
  • Female
  • Horse Diseases / diagnosis
  • Horses
  • Neoplasms, Unknown Primary / veterinary

Conflict of Interest Statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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Citations

This article has been cited 1 times.
  1. Barrantes Murillo DF, Cattley RC, Cullen JM, Withers C, Towns J, Pfeifle R, Wooldridge A, Neto RLALT. Intrahepatic mucinous cholangiocarcinoma with recurrent colic in a horse case report and literature review of cholangiocarcinoma in horses. J Vet Diagn Invest 2024 Jul;36(4):547-553.
    doi: 10.1177/10406387241245775pubmed: 38641993google scholar: lookup
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