Equine osteosarcoma: a series of 8 cases.
Authors: Bush J M, Fredrickson R L, Ehrhart E J
Journal: Veterinary pathology
Summary
# Editorial Summary: Equine Osteosarcoma Case Series Osteosarcoma remains an uncommon neoplastic diagnosis in horses, though most documented cases occur in the mandible of younger animals. Bush and colleagues retrospectively analysed 8 cases presenting to their facility, predominantly affecting male horses aged 7 years or older, with 75% arising in the maxillary or mandibular bones and one case in the proximal tibia. Notably, fibroblastic osteosarcoma was the predominant histological subtype, and none of the horses in this series demonstrated distant metastasis at presentation or during follow-up. Whilst surgical excision was attempted in most cases, incomplete tumour removal typically led to progressive disease and eventual euthanasia, though one extraosseous subcutaneous osteosarcoma caudal to the shoulder achieved successful excision with no recurrence at 14 months post-operatively. The authors emphasise that wider investigation into chemotherapeutic protocols is warranted to improve treatment outcomes, particularly for cases where complete surgical margins cannot be achieved—a reality facing clinicians managing jaw tumours where anatomical constraints limit complete excision.
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Practical Takeaways
- •Osteosarcoma is rare in horses but should be considered in older male horses (7+ years) presenting with mandibular or maxillary swelling; early surgical referral is critical as incomplete excision typically leads to progressive disease
- •Location of the tumor significantly influences prognosis—head-based tumors have poor outcomes with surgery alone, whereas the single extraosseous case had favorable long-term outcome
- •Currently, surgical excision remains the primary treatment option, but the authors advocate for investigation of chemotherapeutic alternatives to improve outcomes beyond euthanasia
Key Findings
- •Equine osteosarcoma predominantly occurs in males aged 7 years or older, with 75% of cases in the maxilla or mandible
- •Fibroblastic osteosarcoma was the predominant histological subtype, with most tumors containing osteoid and chondromucinous matrix
- •No metastasis was identified in any of the 8 horses despite aggressive tumor behavior
- •Surgical excision resulted in disease progression and euthanasia in most cases, though one extraosseous osteosarcoma showed no recurrence at 14 months post-excision