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Peripheral primitive neuroectodermal tumor in a two-year-old paint horse.
Paul R Facemire1, Lynn M Facemire, Shelley P Honnold
1Department of Veterinary Pathology, Armed Forces Institute of Pathology, Washington, DC, USA. paul.facemire@us.army.mil
Summary
A rare peripheral primitive neuroectodermal tumor (PNET) was diagnosed in a 2-year-old gelding. This equine PNET presented with extensive metastasis, highlighting the aggressive nature of this neoplasm.
Area of Science:
- Veterinary Pathology
- Equine Neoplasia
- Oncology
Background:
- Peripheral primitive neuroectodermal tumors (PNETs) are rare in horses, with most previous reports linked to ocular origins.
- This case presents a non-ocular PNET in a young gelding, expanding the known spectrum of this neoplasm in equine patients.
Observation:
- A 2-year-old gelding exhibited lethargy, anorexia, pleural and abdominal effusions, and scrotal masses.
- The horse developed acute dyspnea, leading to euthanasia due to a poor prognosis.
- Necropsy revealed extensive neoplastic infiltration of the scrotum, inguinal canals, peritoneal cavity, kidneys, liver, spleen, mesenteric lymph nodes, mesentery, and diaphragm.
Findings:
- Histological examination showed a neoplasm composed of spindle to round cells with varied arrangements.
- Immunohistochemistry confirmed the diagnosis with positive staining for S-100 protein, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), neurofilament protein (NFP), and synaptophysin.
- The findings supported a diagnosis of peripheral primitive neuroectodermal tumor (PNET).
Implications:
- This case underscores the potential for PNETs to occur in non-ocular locations in horses.
- The aggressive, metastatic nature observed in this case highlights the importance of early recognition and diagnosis of equine neoplasms.
- Further research into equine PNETs may improve understanding and treatment strategies for these rare tumors.
