Understanding Equine Sarcoids: A Guide for Horse Owners 1.0 What is an Equine Sarcoid? An Introduction for Owners An equine sarcoid is the most common type of skin tumor found in horses. While the word "tumor" can be alarming, it's strategically important to understand what a sarcoid is—and what it is not. Sarcoids are not internally metastatic, meaning they will not spread to your horse's lungs, liver, or other organs. However, they are known to be "locally aggressive," capable...