Ocular Squamous Cell Carcinoma (SCC)
Ocular Squamous Cell Carcinoma (SCC)
General description
Squamous cell carcinoma (SCC) is the second most common type of tumor in the horse and the most frequent tumor of the horse’s eye. Factors thought to increase risk for SCC include UV exposure, pigmentation, and genetics. When originating at the limbus, SCC can spread into the cornea, and quickly lead to visual impairment and destruction of the eye.
Breeds
Ardennes horse, Belgian Horse, Belgian Warmblood, Connemara pony, Haflinger, Holsteiner horse, Rocky Mountain Horse
Order details
| Test number | 8292 |
| Abbreviation | SCC |
| Sample material | 0.5 ml EDTA blood, mane/tail hair roots |
| Test duration | 7-14 working days |
Test specifications
| Symptom complex | ophthalmic |
| Inheritance | autosomal recessive |
| Causality | High-risk factor |
| Literature | OMIA:000735-9796 |
Detailed description
The squamous cell carcinoma is the most common cancer of the equine eye (Ocular Squamous Cell Carcinoma or SCC). It is characterised by the development of a tumour (mass formation) on the eye. When the tumour arises at the limbus — the junction between the cornea and the sclera, visible as the dark border of the iris — the SCC can quickly spread into the cornea and lead to visual impairment and destruction of the eye. Various factors are responsible for the development of a squamous cell carcinoma.
In Haflingers and related breeds, a risk factor (DDB2 gene) has been identified, which can be detected through a genetic test. For horses that carry this gene in a homozygous state, regular eye examinations are recommended for early detection and improved prognosis. In addition, wearing a fly mask to provide UV protection is advisable, as UV exposure from intense sunlight, together with pigmentation, represents another risk factor for the development of this condition.
In a Haflinger that is homozygous for the risk gene, SCC occurs 5.6 times more frequently, and in the Belgian breed 4 times more frequently, than in animals of the same breed that do not carry the gene or carry it only in a heterozygous form.
Furthermore, the homozygous genotype has also been identified in horses of the Rocky Mountain Horse, Connemara Pony, and Holsteiner/Belgian Warmblood cross breeds that presented with squamous cell carcinoma of the eye.
