Equine sarcoids: A clinicopathologic study of 49 cases, with mitotic count and clinical type predictive of recurrence.
Authors: Karalus Wilson, Subharat Supatsak, Orbell Geoff, Vaatstra Bernie, Munday John S
Journal: Veterinary pathology
Summary
# Equine Sarcoids: Identifying High-Risk Cases Through Histopathology Sarcoids represent one of the most frequently encountered skin tumours in horses, yet clinicians have previously lacked reliable histological markers to predict which lesions will recur following surgical removal. Wilson and colleagues examined 49 surgically excised sarcoids with known recurrence outcomes, evaluating five histopathological variables (mitotic count, cellularity, necrosis, nuclear pleomorphism, and inflammation) alongside clinical classification. Two factors emerged as significant predictors of recurrence: sarcoids with a mitotic count ≥20 per 2.37 mm² showed an 80% recurrence rate compared to just 18% in those with lower counts, and fibroblastic-type sarcoids recurred in 75% of cases versus 18% for other clinical types. Cox regression analysis confirmed both elevated mitotic activity and fibroblastic morphology as independent risk factors for recurrence (P = .005 and P = .016 respectively). For equine practitioners, these findings offer the first evidence-based histopathological framework for stratifying sarcoid risk: lesions combining high mitotic activity and fibroblastic presentation warrant particularly aggressive initial management and closer post-operative monitoring, potentially influencing decisions around adjunctive therapies, follow-up intervals, and realistic recurrence counselling for owners.
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Practical Takeaways
- •Request histopathology with mitotic count assessment on all surgically excised sarcoids to identify high-risk cases (MC ≥20) requiring closer monitoring or alternative treatment approaches
- •Fibroblastic sarcoids carry substantially higher recurrence risk (75%) and may warrant more aggressive surgical margins, adjunctive therapies, or owner counselling about recurrence likelihood
- •For low-risk sarcoids (non-fibroblastic type, MC <20), standard surgical excision appears adequate with 82% success rate, though long-term monitoring remains important
Key Findings
- •Overall recurrence rate was 24% (12 of 49 cases) following surgical excision
- •Sarcoids with mitotic count ≥20 per 2.37 mm² had 80% recurrence rate versus 18% for those with mitotic count <20 (P=0.0051)
- •Fibroblastic clinical type showed 75% recurrence rate compared to 18% for other types (P<0.001)
- •Mitotic count ≥20 and fibroblastic type were significant independent predictors of recurrence on Cox regression analysis