Squamous Cell Carcinoma in a Horse’s Tongue: Symptoms, Diagnosis, and Prognosis

Clinical Case: Tongue Squamous Cell Carcinoma in a Draft Horse

In the spring of 2023, a 16-year-old Belgian draft horse was referred to our clinic for follow-up of a previously identified tongue lesion. The owner had already been monitoring dental issues, but in recent months noticed increasing drooling, reduced appetite, and bloody saliva.

During our clinical examination, we observed a large lesion on the tongue. Initially, trauma or a foreign body was suspected, but due to the persistent nature, the size of the lesion, and the absence of any foreign object on exploration or radiography, we proceeded with a biopsy and CT imaging.

Imaging and Histopathology Results of Equine Tongue SCC

The CT scan of the head revealed significant abnormalities:

• A large mass (10.3 x 6.4 x 6 cm) in the tongue with an ulcerated defect on the right side (up to 9 cm long and 4.4 cm deep)

• Severe enlargement of the medial retropharyngeal and mandibular lymph nodes, indicating lymphatic metastasis

• Narrowing of the pharynx due to both the swollen lymph nodes and the enlarged tongue mass

• Thickening of the soft palate

Histopathological analysis confirmed the diagnosis: a locally aggressive squamous cell carcinoma (SCC) of the tongue with clear metastasis to regional lymph nodes. Due to the extent and aggressiveness of the condition, euthanasia was considered the most humane option and was performed on June 12, 2023.

What Is Squamous Cell Carcinoma (SCC) in Horses?

SCC is a malignant tumor originating from squamous cells—the building blocks of skin and mucous membranes. In horses, this tumor more commonly occurs in the eyes, nose, and genitals. Its presence in the tongue or oral cavity is extremely rare.

Only isolated cases are reported in the literature. Routt et al. (1981) described an SCC at the base of the tongue in a horse with symptoms such as difficulty swallowing, excessive salivation, and oral ulcers. In that case too, treatment was impossible due to infiltration and metastasis.

Can Equine Viruses Cause Squamous Cell Carcinoma?

Recent studies have investigated the role of Equus caballus papillomavirus type 2 (EcPV2) in the development of SCC in horses, especially in genital and head-neck regions.
In our patient, no virological testing was performed, but the rapid progression and invasiveness were more indicative of a non-viral, spontaneous SCC.

Diagnosis and Treatment Options for SCC in Horses

Why Early Detection of Tongue Cancer in Horses Matters

The case teaches us that signs such as chronic drooling, blood in the mouth, or difficulty eating should not be taken lightly. Early biopsy and imaging can be critical for timely diagnosis.

Therapeutic Challenges of Treating SCC in Equine Tongues

Once SCC involves the tongue with local invasion and metastasis, surgical or medical treatments are generally ineffective or unfeasible in horses. Unlike in human medicine, radiotherapy and chemotherapy are rarely available or practical in veterinary care for large animals.

Final Thoughts: Lessons from a Rare Case of Oral SCC in Horses

This case was painful, but instructive. Squamous cell carcinoma of the tongue is a rare and aggressive tumor in horses, often only recognized in advanced stages. In case of persistent or progressive oral lesions, we recommend early referral and targeted diagnostics.

‍⚕️ Are you a veterinarian and would like to consult on a similar case? Don’t hesitate to contact us. Together, we ensure rapid and compassionate care for every horse.

FAQ

1. What is a squamous cell carcinoma in the tongue of a tract horse?
A squamous cell carcinoma (SCC) is a malignant tumor arising from squamous cells. In the tongue, it may cause eating difficulties, excessive saliva, swelling, or nerve impairment.

2. What are the symptoms of a tongue tumor?
Symptoms include: difficulty chewing, drooling, weight loss, swelling in the mouth, foul odor, abnormal lesions, or a visible mass on the tongue.

3. How is a tongue SCC treated, and what is the prognosis?
Treatment typically involves surgical removal (not possible for the tongue), sometimes followed by radiation therapy or chemotherapy. The prognosis depends on tumor size, location, and aggressiveness — early detection significantly improves chances of a favorable outcome.