Vetdle Archive Case #119: Equine Melanoma

Clinical Clues

An older horse is presented for slowly enlarging skin nodules.
The masses have changed gradually over the past year without making the horse systemically ill.
Several nodules are clustered beneath the tail and around the perineum.
The horse is grey and the masses are darkly pigmented.
Pigmented skin tumours are especially common in ageing grey horses.
Equine melanoma frequently develops as black masses under the tail in older grey horses.

Diagnosis

Equine Melanoma

This case is most consistent with Equine Melanoma because the horse is grey and has typical slowly enlarging black perineal masses. The most important clues are the coat color and lesion location, which make a simple wart or sarcoid 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 Melanoma, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

Clue 1: An older horse is presented for slowly enlarging skin nodules.
Clue 2: The masses have changed gradually over the past year without making the horse systemically ill.

Clues 3-4

Clue 3: Several nodules are clustered beneath the tail and around the perineum.
Clue 4: The horse is grey and the masses are darkly pigmented.

Clues 5-6

Clue 5: Pigmented skin tumours are especially common in ageing grey horses.
Clue 6: Equine melanoma frequently develops as black masses under the tail in older grey horses.

Self-review prompts

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

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.