Peer-reviewed veterinary case report
Disseminated pleomorphic rhabdomyosarcoma in a horse.
- Journal:
- Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc
- Year:
- 2025
- Authors:
- Carpenter, Alexis L et al.
- Affiliation:
- Department of Veterinary Pathobiology · United States
- Species:
- horse
Plain-English summary
An 8-year-old mare, which is a National Show Horse, was brought in because she was having trouble with pneumonia and laminitis, a painful condition affecting her hooves. During the examination, the vet found abnormal lung sounds and signs of pain in her hooves. Unfortunately, her health quickly worsened, and she was put to sleep to prevent further suffering. A postmortem examination revealed multiple firm, tan nodules in her lungs and other organs, and tests showed that these were cancerous cells consistent with a rare type of cancer called pleomorphic rhabdomyosarcoma. Sadly, the treatment options were not effective, and the mare's condition was terminal.
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.
Find similar cases for your pet
PetCaseFinder finds other peer-reviewed reports of pets with the same symptoms, plus a plain-English summary of what was tried across them.
Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/39301962/