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→ A malignant tissue formation (tumor) that develops from the superficial layers of the skin and mucous membranes.


  • Slowly growing malignant skin neoplasms.
  • Especially mucous membranes are affected.
  • Development of eye cancer.
  • Impairment or loss of the eye.

General Information:

  • Most common type of eye cancer in horses.
  • This test identifies a gene mutation that increases the risk of developing a SCC. → Risk Test
  • Due to this mutation in the DNA, the DDB2 protein, which is responsible for DNA repair in UV light damage, is not correctly formed.
  • SCC is particularly common in Haflinger Horses due to the frequent occurrence of this mutation in the breed.
  • It has also been described in Belgian draft horses and Pecherons.

Inheritance: autosomal recessive

→ The risk of developing SCC is increased if both copies of the gene (scc/scc) are affected by the mutation. Animals with only one copy (N/scc) are clinically normal carriers.

Possible Genotypes:

Genotype: The horse is/has:
N/N normal. The horse has no copies of the genetic variant causative for SCC and therefore cannot pass it on to its offspring.
N/scc a carrier. The horse is clinically healthy. The genetic variant causative for CSS will be passed on to its offspring with a probability of 50%.
scc/scc a risk. The horse has an increased risk of developing SCC. The mutation will be passed on to its offspring with a probability of 100%.



  • Carriers may be bred to normal animals (N/scc x N/N) without any risk of producing at risk offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • When breeding two carriers (N/scc x N/scc), there is a probability of 25% for each foal to inherit two copies of the mutation (scc/scc) and therefore having an increased risk of developing SCC. This should be taken into consideration when planning breedings.

Test information: This test detects a missense mutation im DDB2gene (c.1013 C > T p.Thr338Met).

Bellone, R.R., Liu, J., Petersen, J.L., Mack, M., Singer-Berk, M., Drögemüller, C., Malvick, J., Wallner, B., Brem, G., Penedo, M.C., Lassaline, M. : 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 :, 2017. Pubmed reference: 28425625. DOI: 10.1002/ijc.30744.

Singer-Berk, M., Knickelbein, K.E., Vig, S., Liu, J., Bentley, E., Nunnery, C., Reilly, C., Dwyer, A., Drögemüller, C., Unger, L., Gerber, V., Lassaline, M., Bellone, R.R. : Genetic risk for squamous cell carcinoma of the nictitating membrane parallels that of the limbus in Haflinger horses. Anim Genet :, 2018. Pubmed reference: 29999543. DOI: 10.1111/age.12695.

Further information is available at Online Mendelian Inheritance in Animals.

Breeds affected:

Test #: H126

Samples: Blood, Hair

Price: 35 € (net)

Time required: 10-14 days

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