Vet Tips 2025: Squamous Cell Carcinoma in Horse Eyelids—Early Detection Is Key 🐴👁️

By Dr Duncan Houston BVSc

Horses with light-colored faces and unpigmented skin around their eyes are more susceptible to developing a serious condition—squamous cell carcinoma (SCC). This common cancer, similar to “cancer eye” in cattle, is the most frequently diagnosed tumor on the eyelids of horses. 👁️🧬

What Is Squamous Cell Carcinoma (SCC)? 🧠🔬

SCC is a malignant tumor that develops in the epithelial cells of the skin and mucous membranes. In horses, it’s often found:

• 👁️ On the eyelids
• 👀 On the cornea
• 🩺 On the third eyelid or conjunctiva

Though it may begin as a small, red, inflamed bump, it can grow rapidly and eventually impair or destroy the eye. 👁️💥

Who's at Risk? ⚠️🐴

Some horses are more prone to this condition due to their appearance and environment. Risk factors include:

• ☀️ High UV exposure (especially in sunny climates)
• 🐴 Horses with light-colored or white facial markings
• 👁️ Unpigmented skin around the eyes

Prevention starts with awareness—watch those light-colored horses closely, especially in the spring and summer. 🕶️

Early Signs to Watch For 🔍👁️

Squamous cell carcinoma can mimic less serious eye conditions, such as allergies or conjunctivitis. Look for:

• 🟥 Small red or inflamed areas on the eyelid or third eyelid
• 💧 Excessive tearing, usually from one eye
• 🧱 Skin thickening or crusting near the eye
• 📈 Rapid growth or change in appearance of eye tissue

Don't wait—call your vet at the first sign of any unusual eye inflammation or discharge. 👩‍⚕️

Diagnosis and Biopsy 🧪📋

Though SCC can often be suspected based on appearance, a biopsy is required to confirm the diagnosis. Your vet may:

• 🧫 Collect a small tissue sample under local anesthesia
• 🩺 Rule out infections, dust allergies, or other causes
• 📈 Evaluate tumor size, depth, and invasiveness

Timely biopsy leads to faster treatment and better outcomes. 🏥

Treatment Options for SCC 👨‍⚕️💉

Multiple treatments are available depending on the tumor’s location, size, and aggressiveness. These include:

1. Surgical Removal 🔪

• ✅ Best for small, localized tumors
• ⚠️ May not be possible in all eye regions without functional or cosmetic compromise

2. Cryotherapy (Freezing) 🧊

• 🧊 Targets cancer cells by freezing tumor tissue
• 🚨 Useful after surgery to reduce recurrence

3. Chemotherapy 💉

• 💊 5-Fluorouracil (5-FU): Injected directly into the tumor to shrink it
• 🧠 May not cure but helps reduce tumor mass for surgical removal or symptom relief

4. Radiotherapy 🔆

• 💡 Used in severe or recurrent cases
• 🧬 Often used at specialized veterinary centers

5. Hyperthermia 🌡️

• 🔥 Controlled heating to destroy cancer cells
• 📈 Still under study but has shown promising results

Can SCC Be Prevented? 🛡️☀️

While not fully preventable, risk can be reduced:

• 🕶️ Use fly masks with UV protection, especially for light-faced horses
• ⛅ Provide shade during peak sunlight hours
• 🔍 Monitor for early signs and schedule routine eye checks

When to Call the Vet 📞🐴

Contact your vet if you notice:

• 🩸 Bleeding or ulcerated masses near the eye
• 💧 Persistent tearing or discharge from one eye
• 🔴 Sudden bumps or discoloration near the eyelids

Early intervention = more treatment options and less trauma. ⏱️

Need Support With an Eye Tumor? Ask A Vet 📱🐴

Whether your horse has eye inflammation or you’re facing a confirmed SCC diagnosis, get expert advice via Ask A Vet.

Download the Ask A Vet app for 24/7 equine care support—including second opinions, biopsy interpretation, and custom treatment planning. 🐎📲

Final Thoughts: Don’t Blink on Eye Health 👁️🐴

Squamous cell carcinoma is common—but treatable when caught early. Know your horse’s risk factors, monitor for eye changes, and work closely with your vet for the best outcome. 🎯

Questions about eye swelling or eyelid bumps? Visit Ask A Vet for guidance you can trust. 🩺🐴