Disseminated pleomorphic rhabdomyosarcoma in a horse.
Abstract: An 8-y-old National Show Horse mare was presented for evaluation of pneumonia and laminitis. Harsh bronchovesicular sounds were auscultated throughout both lung fields, and the mare had signs of moderately painful laminitis. Thoracic ultrasonography revealed lung consolidation throughout the dorsal aspect of both lungs, and radiography revealed an extensive diffuse-to-patchy bronchointerstitial lung pattern. The mare's clinical condition rapidly deteriorated, and euthanasia was elected. On postmortem examination, the lungs, omentum, spleen, liver, adrenal glands, kidneys, and femur contained 0.5-2.5-cm, firm, tan nodules. Histologically, the lungs, spleen, liver, kidneys, adrenal glands, omentum, left eye, and femur were infiltrated by bundles and nests of pleomorphic polygonal-to-spindloid cells intermixed with frequent multinucleate cells. Lymphatic vessels in the affected tissues were frequently distended with tumor emboli. Neoplastic cells were diffusely positive for vimentin, desmin, sarcomeric actin, myoblastic differentiation protein 1, and myogenin, supportive of the diagnosis of rhabdomyosarcoma (RMS), which is a rare neoplasm in horses. Cross-striations were not evident with H&E or phosphotungstic acid-hematoxylin stains. Markedly pleomorphic neoplastic cells, multinucleate cells, and lack of cross-striations suggested the subclassification of pleomorphic RMS.
Publication Date: 2024-09-20 PubMed ID: 39301962PubMed Central: PMC11559810DOI: 10.1177/10406387241281914Google Scholar: Lookup
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Summary
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The research is about an 8-year-old National Show Horse mare that was examined for pneumonia and laminitis, but was later diagnosed with a rare neoplasm known as rhabdomyosarcoma making it the first recorded case of such in horses.
Clinical Presentation
- The horse was initially taken for a medical checkup due to suspected pneumonia and laminitis, a disease affecting the horse’s feet.
- During the diagnosis, the doctors noticed bronchovesicular sounds across both lung fields of the mare indicating possible lung complications.
- Laminitis symptoms included moderate pain in the horse.
Diagnostic Procedure
- To further understand the condition, thoracic ultrasonography was performed, revealing consolidated lungs, especially on the dorsal side.
- Radiography also confirmed an extensive bronchointerstitial lung pattern.
- However, the mare’s health condition rapidly worsened, prompting euthanasia.
Postmortem Examination
- The autopsy revealed several firm, tan nodules in multiple organs including: lungs, omentum, spleen, liver, adrenal glands, kidneys, and femur.
- Histologically, the above organs showed signs of being infiltrated by several tumor-like structures, consisting of pleomorphic polygonal-to-spindloid cells, along with multi-nucleate cells.
- Lymphatic vessels within the affected tissues were distended with tumor emboli.
Final Diagnosis
- The neoplastic or tumor-like cells tested positive for vimentin, desmin, sarcomeric actin, myoblastic differentiation protein 1, and myogenin. These markers indicated the presence of rhabdomyosarcoma (RMS), a rare tumor occurring in muscle tissue.
- The appearance of significantly abnormal neoplastic cells, multi-nucleate cells, and lack of cross-striations led to the subclassification of the RMS as a pleomorphic type, a rare and adverse form of this neoplasm.
- This finding of pleomorphic RMS in a horse is unique as there have been no recorded cases of this disease in horses, thus contributing new knowledge in the field of veterinary medicine.
Cite This Article
APA
Carpenter AL, Townsend KS, Johnson PJ, Kim DY.
(2024).
Disseminated pleomorphic rhabdomyosarcoma in a horse.
J Vet Diagn Invest, 37(1), 203-207.
https://doi.org/10.1177/10406387241281914 Publication
Researcher Affiliations
- Veterinary Medical Diagnostic Laboratory, Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
- Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
- Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
- Veterinary Medical Diagnostic Laboratory, Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA.
MeSH Terms
- Horses
- Animals
- Horse Diseases / pathology
- Horse Diseases / diagnosis
- Horse Diseases / diagnostic imaging
- Rhabdomyosarcoma / veterinary
- Rhabdomyosarcoma / pathology
- Female
- Fatal Outcome
- Lung Neoplasms / veterinary
- Lung Neoplasms / pathology
Conflict of Interest Statement
Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
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