🐾 Vet Guide to Testicular Cancer in Dogs: Symptoms, Diagnosis & Treatment Outlook in 2025 🧬

By Dr Duncan Houston, BVSc

Testicular cancer is the most common genital tumor in male dogs, but with early detection and proper treatment, most dogs recover fully and go on to live happy, healthy lives. In this 2025 veterinary guide, I’ll explain the types of testicular tumors, warning signs, diagnostic options, and effective treatments—including why neutering (castration) remains the best solution for a strong cure rate. 🐶

Understanding Testicular Cancer in Dogs 🧠

While testicular tumors in dogs are often malignant (cancerous), their behavior is less aggressive than many other cancers. Here's what makes them unique:

• 📊 Affects mainly senior dogs—average age at diagnosis is around 10 years
• 🧬 Metastasis (spread to other organs) is rare, occurring in only ~15% of cases
• 💉 Cure rate is high with timely surgical removal

Three Common Tumor Types

1. Seminoma: Develops from sperm-producing cells
2. Leydig (interstitial) Cell Tumor: From hormone-producing cells
3. Sertoli Cell Tumor: From sustentacular (support) cells—can secrete estrogen

Multiple types may appear in the same testicle, and both testicles can be independently affected. 🔬

Signs and Symptoms to Watch For 🔍

Many dogs with testicular tumors show no symptoms at first, so early detection depends on careful observation and regular vet exams. Key signs include:

• 🔴 Enlarged, firm, or asymmetrical testicles
• 😣 Testicular pain or tenderness
• 🧽 Weight loss or poor appetite
• 😴 Lethargy or disinterest in usual activities

Hormonal Effects of Tumors

Sertoli cell tumors can cause estrogen production, leading to:

• 🌸 Enlarged nipples or mammary glands
• 🐾 Hair loss on the flanks or trunk
• ⚫ Darkened skin patches
• 🩸 Anemia, bleeding issues, or infection (due to bone marrow suppression)

Leydig cell tumors may cause testosterone-related symptoms, including:

• 🍑 Swelling near the anus from perianal gland enlargement or hernias

Cryptorchid Dogs (Undescended Testicles)

If your male dog appears to have only one testicle, the other may be retained inside the abdomen—a condition called cryptorchidism. These retained testicles are at much higher risk for developing cancer (especially seminomas or Sertoli tumors). Because they are hidden, diagnosis is often delayed. 🧪

How Is Testicular Cancer Diagnosed? 🧫

When testicular cancer is suspected, your veterinarian will perform the following:

1. Physical & Rectal Exam

• 🖐️ Check size, shape, and consistency of both testicles
• 👆 Examine prostate gland and lymph nodes via rectal exam

2. Imaging

• 🩻 X-rays: Detect spread to lungs or abdominal organs
• 🔬 Ultrasound: Useful for cryptorchid testicle location and organ evaluation

3. Blood Tests

• 🧪 Assess organ function and hormone levels
• 🩸 Detect anemia, low platelets, or white cell irregularities

4. Biopsy/Pathology (Post-Surgery)

After testicle removal, a pathologist examines the tissue to confirm cancer type. This determines whether further treatment is needed. 🎯

Treatment: Why Castration Is the Gold Standard ✂️

The recommended treatment for testicular cancer in dogs is neutering (castration)—removal of both testicles:

• ✅ Eliminates the cancer source
• 💪 Simple surgery with rapid recovery
• 🎯 Often curative, especially when no metastasis is present

Castration for Cryptorchid Dogs

For dogs with an undescended testicle:

• 🔍 Exploratory abdominal surgery may be needed
• 🛠️ Both testicles must be removed—cancer can affect either or both

Additional Therapies

• 💉 Chemotherapy: Sometimes used in advanced or metastatic cases
• 🔆 Radiation: May be considered in select scenarios

Referral to a veterinary oncologist is recommended if your primary vet suggests these therapies. 🧑‍⚕️

Prognosis: What to Expect 📈

Excellent with Early Detection

• 🏥 Surgery alone is often curative
• 📉 Only ~15% of testicular cancers metastasize
• 🔁 Routine checkups increase early detection odds

Poorer Outlook in Advanced Cases

• 🧬 Dogs with bone marrow suppression or hormone-driven illness may not recover fully
• 🕒 Earlier surgery improves chances of survival

Preventing Testicular Cancer in Dogs 🚫

Neutering your male dog—especially if he's not used for breeding—is the best preventive measure. Benefits include:

• 🐕 Elimination of testicular cancer risk
• 😌 Reduced risk of prostate disease and perianal tumors
• 🧠 Behavioral benefits in some dogs (e.g., less roaming or marking)

Even in older dogs, neutering remains beneficial if cancer is suspected or confirmed. 💉

Final Thoughts from Dr Duncan Houston 👨‍⚕️

Testicular cancer is common, but also one of the most treatable cancers in dogs. In most cases, neutering resolves the issue completely—especially when the condition is diagnosed early. If you notice any changes in your dog's testicles, appetite, or energy level, don’t wait—have them checked out right away.

Need help deciding what’s best for your dog? Visit Ask A Vet or download the Ask A Vet app to connect with licensed vets 24/7 for trusted support. 📱🐾