Squamous Cell Carcinoma (SCC)


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Squamous Cell Carcinoma (SCC)


Squamous cell carcinoma (SCC) is the most common cancer affecting the equine eye. At an increased risk of developing this disease are Appaloosas, paints, pintos, Haflingers, (Belgians, Shires, and Clydesdales) and any horse lacing pigment in or around the eye.


Research has shown that a recessive DDB2 missense variant C>T can be used as a risk factor for developing SCC. Roughly 88% of the cases studied were homozygous for the variant.

Breeds Affected:

Testing for SCC is valid for Haflinger and Belgian breeds, and may also be tested in Percherons. Current list will be updated if other breeds are validated.

Test Results:

R/R At Risk The horse carries two copies of the variant and is homozygous for the mutation. The horse has a higher likelihood of developing limbal squamous cell carcinoma (SCC).
N/R Carrier Both the normal and mutant alleles were detected. Horse tested heterozygous and is a carrier of the gene mutation.
N/N Clear Horse tested negative for the variant and does not carry the gene mutation. The horse will not pass on the defective gene to its offspring.

    Submit a Sample for Testing:

    To submit a sample for testing please click on ORDER and download a sample submission form. Then follow the sample collection and submission instructions.


    Cost per sample is $40.00. Please see our Equine Fee Schedule for all equine testing rates.


    Bellone RR, Liu J, Petersen JL, Mack M, Singer-Berk M, Drögemüller C, Malvick J, Wallner B, Brem G, Penedo MC, & Lassaline M. (2017) A Missense Mutation in Damage-specific DNA Binding Protein 2 Is a Genetic Risk Factor for Limbal Squamous Cell Carcinoma in Horses. Int. J. Cancer 141(2):342-353.

    Lassaline M, Cranford TL, Latimer, CA, & Bellone R. (2015) Limbal squamous cell carcinoma in Haflinger horses. Vet Ophthalmol 18(5) 404-408.