Squamous cell carcinoma

Veterinary advice should be sought before applying any treatment or vaccine.

Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is the second most common type of skin cancer in horses, and one of the most frequent forms of cancer affecting the eye. SCC tumors appear as solitary, raised, irregular masses, often ulcerated or infected, that develop around the eyelids (and third eyelids), genitals, face and ears, anal region, and other areas with minimal hair coverage and pigmentation. SCC tumors are slow-growing and are found most often in horses with white faces or markings that extend around the eyes.

Despite a large amount of research conducted on treatment for SCC, it is still a challenging condition to treat. The location of the tumor largely influences the type of treatment used. There are a wide range of currently available treatment options, however some are not universally accepted or supported by evidence based on clinical practice.


Raised, irregular masses found around the eyes, lips, nose, anus, or genitals


  • History
  • Clinical signs
  • Physical exam
  • Biopsy



Surgical removalInvolves removal of the affected tissue or the eye.
CryotherapyLiquid nitrogen is used to freeze the lesions off.
ChemotherapyInjected into the mass or used topically. Cisplatin or five-fluorouracil (5-FU)
Mitomycin-CAn antimicrobial with anti-tumor properties.
CO2 laserUsed for small lesions.
Photodynamic therapyThe injection of a photosensitive agent into the lesion that is passed over with a small laser with a specific wavelength
Oral piroxicamAn anti-inflammatory used for treatment of ocular SCC or in combination with other treatments.
Irradiation therapyapplied by using beta irradiation or brachytherapy implants. It is commonly used after surgical debulking. The side effects of this therapy include keratitis and anterior uveitis. The success rate of this treatment is 80% no reoccurrence during the first year, and 70% the second year.
Radiofrequency hyperthermiaThis therapy is recommended on tumors that are less than 3 mm deep and 4 cm in diameter, as these are the limits of radiofrequency. Potential complications include ulcerative keratitis, conjunctivitis, and anterior uveitis.



Poor without complete removal.

Scientific Research

Clinical Trials

  • Squamous cell carcinoma near e icon
  • squamous cell carcinoma icon
  •  icon
  •  icon

Age Range

SCC is found most commonly in older, light colored horses on unpigmented areas of the body.

Risk Factors

  • Horses with white faces or markings that extend around the eyes.

Commonly Affected Breeds

Appaloosa iconClydesdale iconPaint Horse icon