Equine Oncology: Melanoma, Squamous Cell Carcinoma, and Sarcoids; Treatment Options for Solid Tumors

Etiology: In most horses, the origin of melanocytic tumors is NOT thought to be related to sun exposure. In grey horses, the gene associated with “graying” leads to increased risk of tumor formation. This gene is referred to as STX17 and copy-number expansion of the gene has been linked to the grey horse color and increased expression of melanocytic genes. Furthermore, there are specific SUBSETS of grey horses that have mutations in the agouti gene (gene responsible for bay colored horses) that further increase risk for tumor formation and may contribute to the generalized melanomatosis presentation. These mutations are inherited in an autosomal dominant fashion and can be tested for.