Squamous Cell Carcinoma

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Also Known As

Skin Cancer


Squamous cell carcinoma most often affects the skin, eyes, and genital system of the horse, although it may affect the stomach and other organs. The carcinoma begins as a wart-like growth or a flat lesion with a yellow, infected-looking base. As it grows, it becomes nodular and fleshy and bleeds easily. 


  • Wart-like growth or lesion with yellowish base
  • Small nodules
  • Ulcerated areas with a foul odor
  • Anorexia
  • Weight loss
  • Lethargy
  • Abnormal chewing and swallowing behavior
  • Anemia


Ultraviolet light exposure and lack of pigment are thought to be the primary predisposing factors for squamous cell carcinoma. The incidence of the cancer is higher in southern and western areas and in areas of increased altitude or solar radiation.

Squamous cell carcinomas arise from epidermal cells and are often invasive, but tend to be slow to spread or metastasize. When metastasis does occur, lymph nodes are generally the affected sites carrying cancer cells to other parts of the body.


To date, no effective prevention is known. Early recognition of squamous cell carcinoma and effective treatment by a qualified veterinarian often prevent the cancer from metastasizing and improve the chances for a positive outcome.


Diagnosis of squamous cell carcinoma is usually done by biopsy. Any growth that appears to be squamous cell carcinoma should receive prompt treatment. Treatment usually involves local excision, if the excision can be done without damaging vital structures.

Radiation therapy that involves implanting radon probes into the cancer, thereby reducing the size of the tumor and making it easier to remove, is used effectively by some veterinarians.

Cryotherapy, or freezing of the tumor after debulking it to a smaller size, works well in many cases. .

Radiofrequency hyperthermia with radio waves transmitted through probes inserted into the tumor destroys the cancer cells using heat.

In some cases, intra-lesional chemotherapy or carbon dioxide laser ablation is used. Excision alone is often not sufficient and most veterinarians recommend ancillary therapy.

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EquiMed staff writers team up to provide articles that require periodic updates based on evolving methods of equine healthcare. Compendia articles, core healthcare topics and more are written and updated as a group effort. Our review process includes an important veterinarian review, helping to assure the content is consistent with the latest understanding from a medical professional.