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Archive Case #61: Equine Sarcoid

Horse veterinary case - Easy - May 3, 2026

Clinical Clues

  1. A horse is presented for a persistent skin mass at the site of an old superficial wound.
  2. The lesion has slowly enlarged over several months and repeatedly ulcerates after being knocked.
  3. It is locally invasive in appearance but does not behave like a simple proud flesh lesion.
  4. The mass is fibroblastic with an irregular wart-like surface.
  5. These lesions are commonly associated with bovine papillomavirus exposure in horses.
  6. Equine sarcoid is the most common skin tumour of horses and often recurs after incomplete treatment.

Diagnosis

Equine Sarcoid

This case is most consistent with Equine Sarcoid because the horse has a chronic fibroblastic skin mass at a trauma site with typical local behaviour. The most important clues are the irregular wart-like lesion and its persistent recurrent nature, which make exuberant granulation tissue less likely.

Learning review

Review the case evidence

Use the paired clues to explain how the evidence in this horse case supports the provided diagnosis, Equine Sarcoid, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

  1. Clue 1: A horse is presented for a persistent skin mass at the site of an old superficial wound.
  2. Clue 2: The lesion has slowly enlarged over several months and repeatedly ulcerates after being knocked.

Clues 3-4

  1. Clue 3: It is locally invasive in appearance but does not behave like a simple proud flesh lesion.
  2. Clue 4: The mass is fibroblastic with an irregular wart-like surface.

Clues 5-6

  1. Clue 5: These lesions are commonly associated with bovine papillomavirus exposure in horses.
  2. Clue 6: Equine sarcoid is the most common skin tumour of horses and often recurs after incomplete treatment.

Self-review prompts

  1. After clues 1-2, what evidence from this horse case shaped your initial interpretation?
  2. When you compare clues 3-4 with clues 1-2, what changed in your reasoning about Equine Sarcoid?
  3. How do clues 5-6 align with the case explanation for Equine Sarcoid?

Educational Use

Vetdle archive cases are educational veterinary games for diagnostic reasoning practice. They do not provide veterinary advice, diagnosis, treatment, or professional medical guidance.