강아지 호르몬 반응성 종양(프로게스테론) 자주 묻는 질문 Q&A — 보호자가 꼭 알아야 할 핵심

What Are Hormone-Responsive Tumors in Dogs? — Essential Q&A for Progesterone and Neutering Owners

Oncology/CancerQ&AMeongsiljang Veterinary Advisory Board

Hormone-responsive tumors in dogs are growths that develop in response to progesterone, and they primarily affect older female dogs. Early detection and appropriate treatment are essential.

What Are Hormone-Responsive Tumors (Progesterone) in Dogs?

Diagram of a female dog’s reproductive anatomy, with a tumor indicated near the ovary

In dogs, progesterone levels can rise naturally during the diestrus phase of the estrous cycle or when progestin medications are administered. Textbooks report that progesterone at this stage stimulates the proliferation of mammary ductal epithelium and the secretion of growth hormone. This hormonal environment can be associated with changes in the mammary glands, particularly in intact females, especially older dogs. Drugs that block progesterone receptors (e.g., aglepristone) are known, and in some cases, hormone-based approaches may be attempted. However, since the actual nature of the tumor must be confirmed through testing, a tissue biopsy and ultrasound examination are necessary for an accurate diagnosis. Early detection and appropriate evaluation significantly influence prognosis.

What Are the Main Causes of This Tumor?

In dogs, progesterone levels rise naturally during the luteal phase of the estrous cycle or can be elevated by administering progestin medications. Textbooks report that progesterone at this stage induces proliferation of the mammary gland ductal epithelium and excessive secretion of growth hormone. Intact females (those not spayed via ovariohysterectomy) may experience repeated exposure to progesterone with each estrous cycle. As dogs age, this hormonal exposure can accumulate, and progesterone levels also rise during diestrus even in non-pregnant cycles. Therefore, spaying is considered a method to reduce such hormonal stimulation. However, the actual risk for each individual dog should be assessed by a veterinarian based on test results and clinical condition.

Female dogs' reproductive hormone cycles and tumor development during periods of elevated progesterone

What Symptoms Appear?

If your dog has progesterone-related mammary or reproductive tract tumors, you may notice the following changes:

Swelling at the tumor site: You might feel lumps in the mammary glands or abdomen.

Bleeding or discharge: There may be blood or mucous discharge from the reproductive organs.

Changes in appetite and weight: If the overall health is affected, appetite and weight may change.

Decreased activity level: A drop in condition may lead to less movement than usual.

Systemic effects: As the tumor grows or spreads, it can impact the function of other organs.

If you observe any of these changes, please do not make a diagnosis on your own—bring your pet to the clinic for a proper examination.

A puppy with a tumor mass and discharge on its abdomen

Signs Requiring Immediate Veterinary Visit

If the tumor grows rapidly, bleeding worsens, or your pet appears to be struggling to breathe, seek veterinary care immediately. While some tumors can become malignant or metastasize, the likelihood varies depending on the type of tumor, so please consult your veterinarian rather than trying to assess the situation on your own.

How Is Diagnosis Performed?

Diagnosing hormone-responsive tumors in dogs involves several tests.

Ultrasound: Accurately determines the tumor’s size and location.

Blood tests: Check hormone levels and overall health status.

Biopsy: A key test to determine the nature of the tumor.

CT/MRI: Used to check if the tumor has spread to other organs.

These tests are comprehensively analyzed to make an accurate diagnosis.

A veterinarian performing an abdominal ultrasound on a puppy, with a tumor image visible on the screen.

What Are the Treatment Options?

Treatment for hormone-responsive tumors in dogs varies depending on the tumor’s characteristics and location.

Surgical removal: This is the most effective treatment. Complete removal of the tumor reduces the likelihood of recurrence.

Hormonal therapy: If surgery is not feasible, administering progesterone blockers can help shrink the tumor.

Chemotherapy: This may be used as an adjunctive treatment if malignant metastasis is suspected.

Radiation therapy: Considered as a localized treatment option, particularly for larger tumors.

Your veterinarian will develop an optimal treatment plan tailored to your dog’s specific condition and circumstances.

A veterinarian performing abdominal tumor surgery on a puppy.

How to Manage at Home?

Proper care at home after treatment can speed up recovery.

Medication adherence: Give your pet the medications exactly as prescribed by your veterinarian.

Diet management: Feed a nutritionally balanced diet and avoid overfeeding.

Activity control: Avoid excessive exercise during the early recovery phase and provide a calm environment.

Regular check-ups: Visit the clinic every 1–3 months after surgery to monitor your pet’s condition.

Stress reduction: Allow your pet to rest comfortably in a quiet space.

These care practices greatly help prevent recurrence.

A puppy resting peacefully in a quiet room, next to its food bowl.

Comparison Table of Treatment Methods

Item	Efficacy	Side effects	When it is appropriate
Surgical removal	High	Low	Pain, recovery period
Hormone therapy	Intermediate	Intermediate	Hormonal imbalance
Chemotherapy	High	High	When metastasis is suspected

The treatment method is determined by the veterinarian based on the tumor's size, location, and whether it has metastasized.

Precautions: Contraindications During Treatment

During hormone therapy, avoid using other hormonal medications concurrently. After surgery, keep the environment clean to prevent infection. Also, if any adverse reactions occur while taking the medication, contact your veterinarian immediately.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Are hormone-responsive tumors in dogs cancerous?

Some tumors can be malignant. However, the nature of the tumor varies by type, so we determine the treatment plan—such as surgery or hormone therapy—after confirming the diagnosis through testing.

Does spaying or neutering help prevent this?

Spaying (ovariohysterectomy) can help lower the risk of hormone-related tumors by reducing exposure to progesterone. The ideal timing and suitability for your pet should be determined through consultation with your veterinarian.

Does hormone therapy need to be administered for a long time?

The duration of treatment varies depending on the medication used and how the tumor responds. Medications such as progesterone receptor blockers are administered according to a set schedule, and your veterinarian will assess your pet’s condition after treatment to determine whether additional therapy is needed.

Is the likelihood of recurrence high?

If the tumor is completely removed through surgery, the likelihood of recurrence is low. However, since hormone therapy alone carries a risk of recurrence, regular check-ups are essential.

Can this tumor be transmitted to other dogs?

No, this tumor is not contagious. It is a hormone-responsive condition and does not spread from dog to dog.

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References

[1] Liptak, J.M. and L.J. Forrest. 2013. 21 – soft tissue sarcomas. In Withrow and MacEwen’s Small Animal Clinical Oncology, 5th edition. R.L. Page, S.J. Withrow, and D.M. Vail, editors. St. Louis: W.B. Saunders.

[2] Preziosi, R. et al. 1995. Histological grading of canine mammary tumors: correlation with clinical outcome. Veterinary Pathology, 32(3), 235–241.

[3] Bray, J.P., R.S. Doyle, and C.A. Burton. 2009. Minimally invasive inguinal approach to perianal gland tumors in dogs. Veterinary Surgery, 38(4), 425–431.