Vulvar Tumors in Dogs: Signs, Diagnosis, and Care

Name: Vulvar Tumors in Dogs: Signs, Diagnosis, and Care
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

A dog tumor on the vulva is a growth on or near the female external genitalia. Some are benign lumps, some are cancerous, and one type is actually spread from dog to dog during breeding. Because the causes and treatments differ so much, any new mass in this area deserves a veterinary exam.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Any new lump, bump, or swelling on or near your dog's vulva should be examined by a veterinarian, because benign and malignant masses can look identical from the outside.
Transmissible venereal tumor (TVT) is a contagious cancer spread by direct contact during breeding, and it is one of the most common vulvar tumors in dogs [1][2].
Diagnosis usually starts with a simple cell sample (cytology) taken from the mass, which can often identify TVT in minutes [1].
Chemotherapy, most often with vincristine, is the treatment of choice for TVT and has a good success rate [1][3].
Other vulvar masses, including benign skin growths and other cancers, are often treated with surgical removal.

What a Mass on the Vulva Actually Is

The vulva is the external opening of the female reproductive tract. Tumors and lumps can develop on the vulvar lips, just inside the opening, or deeper in the vagina where you cannot see them.

The most studied vulvar tumor in dogs is the transmissible venereal tumor, or TVT. It is a naturally transmissible cancer, meaning the cancer cells themselves move from dog to dog through direct contact with the tumor mass [2]. This makes TVT different from almost every other cancer, which starts inside one dog's own cells.

TVT masses often look like cauliflower or a strawberry, and they range from smaller than 5 millimeters to more than 10 centimeters wide [1]. The surface is frequently ulcerated, inflamed, and bleeds easily [1]. Some dogs have a single mass, while others have several [1].

Not every vulvar lump is TVT. Dogs can also develop benign skin growths such as tags and cysts, and they can develop other cancers in this region. A mass on the vulva can also be a sign of a problem deeper in the reproductive tract, so a full exam matters.

If you are also noticing your dog paying unusual attention to the area, our article on Dog Licking Paws And Vulva covers that behavior in more detail.

Signs of a Dog Tumor on the Vulva

What you may see at home

A visible lump, bump, or swelling on the vulva or the skin around it.
Blood spots on the floor, bedding, or carpet, which is a common first sign when the tumor sits deep inside the vagina and you cannot see it [2].
A pink or bloody discharge from the vulva.
Your dog licking the area more than usual.
Straining to urinate or a change in urination habits.
Reluctance to breed or discomfort during mating.

What your veterinarian may find

A mass that bleeds easily when touched [1].
An ulcerated or inflamed surface on the growth [1].
Multiple masses in the genital area, or masses that have spread to nearby skin or to the mouth, nose, or eyes [1].
A mass deep in the vaginal canal that was not visible during a quick look [2].

One important trap: bleeding from a deep vaginal tumor can be mistaken for a urinary problem or a nosebleed, depending on where the blood appears [2]. If your dog has unexplained blood spots, tell your veterinarian exactly where you found them.

Causes and Risk Factors

Transmissible venereal tumor

TVT spreads when a dog's tumor cells contact another dog's mucous membranes, most often during breeding [1][2]. It is not spread through the air or by sharing bowls.

Risk factors identified in a large case-control study include unrestricted outdoor access, which was the strongest predictor of developing the tumor [4]. Mixed-breed dogs, medium-sized dogs, and adult or senior dogs also had higher odds in that analysis [4]. Dogs living in areas with large free-roaming populations face higher exposure risk [4].

Other vulvar masses

Benign skin growths, cysts, and other tumors can appear on the vulva for the same reasons they appear elsewhere on the skin. Age, breed, and individual genetics all play a role. Some cancers in this area are linked to hormones, which is one reason spaying status matters to your veterinarian.

Multiple different tumors can appear at the same time in one dog, which is uncommon but does happen and can make diagnosis tricky [5]. This is one reason a physical exam alone is not enough.

How Veterinarians Diagnose a Lump on the Vulva

The first step: cytology

Your veterinarian will usually start by collecting cells from the mass with a fine needle or a swab and looking at them under a microscope [1]. For TVT, this step often gives a diagnosis right away because the tumor cells have a distinctive appearance.

When more testing is needed

If cytology is not clear, or if your veterinarian suspects a different type of tumor, the next step is usually a biopsy. A tissue sample is sent to a laboratory for histopathology, which identifies the tumor type and whether it is benign or malignant.

Imaging may be recommended to check for tumors deeper in the body. In one reported case, a spayed dog with a history of treated vulvar TVT developed a mass on the uterine stump that was found with ultrasound and CT [6]. That case shows why a veterinarian may look beyond the vulva itself.

Staging

If cancer is confirmed, your veterinarian may recommend blood work, chest X-rays, or other imaging to see whether the tumor has spread. TVT has low metastatic potential, meaning it rarely spreads to distant organs, but it can spread locally to adjacent skin and mucous membranes [1][3].

Situation	Typical first test	Common next step
Visible vulvar mass	Cytology from the mass	Biopsy if results are unclear
Bleeding with no visible mass	Full genital exam	Imaging to look deeper
Confirmed cancer	Staging tests	Treatment plan based on type and stage
Multiple lumps on the body	Cytology of each	Biopsy of the most suspicious

Treatment Options for Vulvar Tumors in Dogs

Chemotherapy for TVT

Chemotherapy is generally considered the treatment of choice for transmissible venereal tumor [1]. Vincristine is the standard drug, and it is usually given as a weekly intravenous treatment [7]. Your veterinarian calculates the exact dose from your dog's body weight and health status, and blood work is typically checked during treatment [7].

The outlook for TVT is good in most cases, except in the rare situations where the tumor has already spread within the body before treatment starts [1].

Surgery

Surgical removal is an option for TVT and is often used along with other treatments [1]. For other vulvar masses, surgery is frequently the primary treatment, especially when the mass is benign or when it can be removed with clean margins.

Surgery may also be needed for tumors in unusual locations. In the case of the uterine stump tumor, the mass was removed through an exploratory abdominal surgery, and the dog was doing well eight months later with no sign of recurrence [6].

Radiation

Radiation treatment can be used for TVT, usually in combination with surgery or chemotherapy [1]. It is less commonly used than chemotherapy for this tumor.

Monitoring only

Some benign lumps, such as skin tags, may only need monitoring. Your veterinarian will tell you whether a watch-and-wait approach is reasonable or whether removal is safer. If you are trying to sort out a small skin growth at home, see Dog Skin Tag or Tumor? How to Tell and What to Do.

Recovery, Outlook, and Long-Term Management

After chemotherapy

Most dogs handle vincristine treatment well, but your veterinarian will monitor blood work weekly during treatment [7]. Remission is confirmed by repeat examination and sometimes repeat cytology.

After surgery

Recovery depends on the size and location of the mass and how the surgery was done. Keep your dog from licking the incision, restrict activity as directed, and go to every recheck. Your veterinarian will decide when the site has healed enough for normal activity.

The chance of recurrence

Recurrence is possible, even after successful treatment. In the reported uterine stump case, the dog had achieved complete remission with a six-month disease-free interval before signs returned [6]. That is why follow-up visits matter even when your dog seems completely normal.

Long-term monitoring

Ask your veterinarian what schedule of rechecks makes sense for your dog. For TVT, periodic genital exams help catch regrowth early. For other tumors, monitoring may include physical exams and imaging.

Some tumors can cause body-wide effects that go beyond the lump itself. Our article on Canine Paraneoplastic Syndromes: Diagnosis and Management explains these indirect effects.

Prevention

Reduce exposure risk

Because TVT spreads by direct contact, limiting uncontrolled roaming and unsupervised breeding contact lowers risk [4]. Street access was the strongest risk factor in one large study, so keeping your dog supervised outdoors is a practical step [4].

Spaying

Spaying removes the uterus and ovaries, which eliminates some hormone-related tumors of the reproductive tract. It does not prevent TVT, because TVT affects the external genitalia and can occur in spayed dogs. The uterine stump case involved a spayed dog, which shows that spaying does not rule out every genital tumor [6].

Regular checkups

A quick genital exam at your dog's annual visit can catch small masses before they grow. If your dog has a history of TVT, tell every veterinarian who examines her, because recurrence can happen months later [6].

Know what is normal for your dog

Check your dog's vulva area during routine grooming or petting. If you feel something new, write down when you first noticed it and how fast it seems to be changing. That information helps your veterinarian decide how urgently to act. For a broader look at evaluating lumps anywhere on the body, see Dog Skin Bumps and Lumps: When to See the Vet.

Limitations and When to Contact a Veterinarian

No article can tell you what a specific lump is. Only a veterinarian who examines your dog and tests the mass can do that. Individual cases need a veterinarian, and the timing below is a general guide.

Contact a veterinarian the same day if:

Your dog has active bleeding from the vulva that does not stop.
A mass appeared suddenly or has grown quickly over days.
Your dog is straining to urinate and cannot pass urine.
Your dog seems painful when the area is touched.

Seek emergency care now if:

Bleeding is heavy or your dog is pale, weak, or collapsing.
Your dog cannot urinate at all despite trying.
Your dog has a large mass that has ruptured or is openly infected.

Schedule a routine visit soon if:

You found a new lump on or near the vulva, even if it seems small.
Your dog has a pink or bloody discharge between heat cycles.
You notice blood spots on bedding or floors with no clear source.
Your dog has a history of TVT and any new sign appears.

Frequently Asked Questions

Can a vulvar tumor in dogs be cured?

Yes, many vulvar tumors can be cured or controlled for a long time. Transmissible venereal tumor has a good outlook with chemotherapy in most cases, unless it has already spread inside the body before treatment begins [1]. Other tumor types depend on the specific diagnosis and how early they are found.

Is a dog tumor on the vulva contagious to other dogs?

Only transmissible venereal tumor is contagious, and it spreads through direct contact with the tumor mass, most often during breeding [1][2]. It is not contagious to people or to other species. Benign lumps and other cancers in this area do not spread between dogs.

Does spaying prevent vulvar tumors?

Spaying prevents some hormone-related tumors of the uterus and ovaries, but it does not prevent transmissible venereal tumor, which affects the external genitalia. A spayed dog can still develop a genital tumor, as shown in a reported case of a uterine stump tumor in a spayed female [6]. Spaying is still worthwhile for many other health reasons.

How fast do vulvar tumors grow in dogs?

Growth speed varies widely by tumor type. Transmissible venereal tumors can range from small to more than 10 centimeters wide, and some grow progressively while others stay steady or even regress [1][8]. A mass that grows quickly over days should be seen promptly.

Will my dog need chemotherapy or surgery?

It depends on the tumor type. Chemotherapy is generally the treatment of choice for transmissible venereal tumor, and surgery may be used along with it [1]. For other vulvar masses, surgery is often the main treatment, especially when the mass can be removed completely.

References

Transmissible Venereal Tumor in Dogs - Dog Owners. Merck Veterinary Manual.
Canine Transmissible Venereal Tumor - Reproductive System. Merck Veterinary Manual.
Canine Transmissible Venereal Tumor: Anatomical Locations, Chemotherapy Response, and Epidemiological Aspects at a Veterinary Teaching Hospital in Brazil (2012-2022). Animals : an open access journal from MDPI, 2025.
Epidemiological determinants of canine transmissible venereal tumor in Northeastern Brazil: Insights from a retrospective case-control analysis. Veterinary and animal science, 2026.
Synchronous Multiple Primary Tumors in a Dog: A Case Report. Case reports in veterinary medicine, 2026.
Transmissible venereal tumor of the uterine stump following successful chemotherapy in a 5-year-old mixed-breed dog. The Canadian veterinary journal = La revue veterinaire canadienne, 2024.
A clinical-cytological scoring system predicts response to vincristine with or without ivermectin in canine transmissible venereal tumor. Journal of veterinary internal medicine, 2026.
Differences in Histopathology and Local Immune Response in Steady and Progressive Natural Transmissible Venereal Tumors in Mexican Dogs. Animals : an open access journal from MDPI, 2026.