Lumps and Bumps, Tumors, Growths, and Cysts on Dogs

Does your dog have a tumor?

Healthy puppy after medical exam
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It's not unusual to find lumps and bumps on dogs, especially as they enter their senior years. Growths and masses can appear on dogs at any age, but they are among the most common health issues seen in older dogs. As a dog owner, it will be helpful for you to understand the different types of lumps, bumps, and growths commonly seen on dogs. However, the most important thing to remember is to seek advice from a trusted veterinarian

What is Dog Growth, Mass, or Tumor?

Most veterinarians will call any unknown lump or bump a growth, mass, or a tumor. These are general terms that do not indicate whether the growth is malignant or benign. These terms all simply mean there is an abnormal growth of tissue that has appeared on or inside your dog that has some type of shape or substance (mass). In general, the terms can be used interchangeably, though some vets prefer one word over the other. Vets may avoid the word tumor when malignancy is not yet known so it is less likely to cause worry for pet owners. Don't panic if your vet says your dog has a mass, growth, or tumor. The next step is to get more information.

How Vets Diagnose Lumps on Dogs

Owners are most likely to find growths on their dogs during routine grooming or while petting their dogs. If you notice a new lump on your dog, contact your vet's office to schedule a visit. After discussing your dog's medical history, your veterinarian will perform a physical examination.

You might not actually notice that your dog has a growth. This is why it's so important to take your dog to the vet for routine wellness exams. Your vet may be able to find a growth while examining your dog's skin and body. Your vet may also be able to feel masses in your dog's abdomen while performing the exam.

Your vet will take a close look at the mass. In most cases, your vet will recommend additional diagnostics to try and determine the type of cells that comprise the mass. This usually means collecting samples of the material inside the mass and analyzing it under a microscope. Your vet typically collects these samples via fine needle aspirate or biopsy. Often, the samples are sent to a lab where a veterinary pathologist can perform a thorough analysis. This test can indicate whether the mass is malignant or benign. If malignant (cancerous) it can determine the type of cancer present.

If your veterinarian finds a tumor, additional diagnostics will most likely be recommended. These diagnostics often include the following:

  • Lab tests such as blood chemistry, complete blood count, and urinalysis
  • Radiographs (X-rays) that can reveal signs of metastasis or other internal abnormalities
  • Ultrasound, which can offer a better view of internal organs and look for metastasis
  • CT scan or MRI, which will help vets get a closer look at the structure of your dog's tumor (if internal) and the internal organs.

Some advanced diagnostics must be performed by a veterinary specialist. Your vet might refer you to a veterinary specialist to get an expert opinion on your dog's case.

Fine Needle Aspirate in Dogs

If the mass can be accessed easily, your vet will likely perform a fine needle aspirate. The FNA is done by inserting a needle into the mass and drawing back into a syringe. A small amount of tissue will usually collect in the needle. Fluid may or may not be collected. Your vet may look at the cells from the needle under the microscope before sending the samples to a laboratory for histopathology.

Sometimes, the FNA does not collect enough cells to get a diagnosis. This does not necessarily indicate an error. When a sample is collected, it's kind of like taking a sample of the inside of a sponge. You may or may not collect a piece of sponge since there are tiny holes. Similarly, there may not be an evenly distributed amount of diagnostic cells throughout the entire tumor.

When Your Dog Needs a Biopsy

If a fine needle aspirate is not effective (or if your vet thinks it's not the best option) the next recommendation is usually a biopsy. A biopsy is often performed with the dog under general anesthesia or sedation, but local anesthesia may be used instead depending on the size and location. The biopsy may be performed by using a special large needle. Or, the vet may cut into the mass surgically. In some cases, the entire mass is removed surgically and sent to a laboratory.

Treatment of Masses, Growths, and Tumors in Dogs

There are a number of different masses that can develop in dogs and all of them cannot be covered in one article. Once again, if you find a growth on your dog or you feel your dog is unwell, seek veterinary attention.

Your dog's treatment will depend on the type and location of the mass. If malignant, surgical removal is often recommended if possible. Cancer treatments such as chemotherapy and/or radiation may be recommended. 

The most common growths found in dogs include skin growths, cysts, oral masses, and lipomas. Dogs may also develop mast cell tumors, mammary tumors, or abdominal masses.

Skin Growths on Dogs

Growths on your dog's skin can be caused by any number of things. It is difficult to know for certain what the growth is without having your vet look at it. Some skin growths are actually related to a skin problem. Certain skin masses are more obvious than others. Any skin growth that grows rapidly, becomes irritated or infected, changes dramatically, or bothers your dog may need to be removed. Your vet is to one to help you decide this. 

  • Sebaceous cysts are common types of skin cysts that contain sebum, a thick, oily material normally found in the skin around the hair follicles. These masses may be found anywhere on the body. Please resist the urge to squeeze skin bumps as this can cause irritation and infection. Sebaceous cysts are benign but can also be mistaken for a malignant tumor called a sebaceous gland adenocarcinoma. 
  • Skin tags on dogs are similar to those humans get. Some can get quite large and pendulous, hanging off the skin by a narrow stalk. Skin tags are benign and are usually not removed unless they bother the dog or get very large and irritated. 
  • Histiocytomas are red bumps that can appear quickly on your dog's skin. Although they are benign tumors, some can grow rapidly and really bother your dog. Your vet may recommend removal of large and/or irritated histiocytomas.
  • Squamous cell carcinoma is a type of tumor that may be caused by sun exposure. This type of cancer can also occur on the skin and/or in the mouth. These tumors often have a pink or reddish color and misshapen, "raw" appearance.
  • Malignant melanoma can occur on the skin and/or in the mouth and is thought to be caused by sun exposure. Many of these tumors have a black color but not all will look the same.

Dog Cysts

Cysts are fluid-filled masses that can be found anywhere on or inside on a dog's body. Many are found on or under the skin. Fortunately, many cysts in dogs are benign. However, malignancy cannot be ruled out until your veterinarian has performed diagnostics. If the cyst does not bother your dog, your vet might leave it alone. Cysts can be periodically drained by your vet but most eventually fill with fluid again. Never attempt to squeeze, pop, or drain a cyst yourself. A cyst can be surgically removed if it bothers your dog and/or your vet recommends removal. Once removed, the cyst should be sent to a lab so a veterinary pathologist can analyze it just in case there are some malignant cells present. 

Canine Oral Growths

There are many kinds of growths that can develop in your dog's mouth. Some growths cannot be seen but will cause signs like bad breath, trouble chewing, difficulty holding things in the mouth, oral pain, and pawing at the face or mouth. Of course, these signs could also indicate dental disease and should not be ignored.

  • Oral papillomas are warts caused by the papillomavirus. They can appear on the dog's lips, face, and inside the mouth. Papillomas are benign but very contagious. They can be removed if they cause problems for your dog, but they will eventually come back.
  • An epulis is an oral growth that usually forms on the gum tissue. Many epulides are benign, but some can be malignant, so further diagnostics are necessary.
  • Gingival hyperplasia is a benign overgrowth of gum tissue that may look a little bit like a tumor in some dogs. This excess gum tissue can be removed if it affecting the teeth. The removed tissue may be sent to a veterinary pathologist just to make sure there are no cancer cells.
  • Squamous cell carcinoma can appear in the mouth and often looks red and irregular.
  • Oral melanoma can occur in the mouth and may be black in color.

Some oral tumors can affect the teeth and bone in the mouth and face. If your dog has an oral mass, your vet will likely recommend putting your dog under anesthesia so a thorough examination and dental radiographs can be done. If there is dental tartar or gum disease present, your vet is also likely to recommend a professional dental cleaning while your dog is under anesthesia.

Lipomas in Dogs

Lipomas are among the most common types of tumors seen in dogs. A lipoma is a benign fatty mass that can be found anywhere on a dog's body, typically under the skin. They usually feel soft and moveable and rarely cause pain or discomfort for the dog. Lipomas can be surgically removed if they interfere with your dog's mobility or comfort, grow rapidly, or rupture (causing skin irritation). In rare cases, an apparent lipoma is actually a malignant tumor called liposarcoma. This is why most vets will recommend FNA of these growths. If the FNA sample just looks like fat, the tumor is considered a benign lipoma.

Mast Cell Tumors in Dogs

Mast cell tumors may appear as small skin bumps or internal tumors. These are often malignant tumors that release histamine when disturbed with tests like a biopsy or FNA. This excess histamine release can have a negative effect on your dog's body, including the heart. If your vet suspects a mast cell tumor, your dog will be treated first with diphenhydramine to minimize the histamine release. Some vets will recommend FNA while others prefer to completely remove suspected mast cell tumors. The pathologist will grade the tumor as I, II, or II. This grading indicates how malignant the tumor is and how likely it is to metastasize.

Mammary Tumors in Dogs

In female dogs, any inflammation of the mammary gland should be addressed as soon as possible. Inflammation of the mammary gland is called mastitis. However, the inflammation may be caused by a tumor. Though some mammary masses may be benign, many are cancerous. Mammary cancer is more common in intact females (not spayed) but can sometimes occur in spayed females.

Abdominal Masses

Some dogs develop abdominal masses, especially as seniors. Abdominal masses are usually found when your dog's abdomen is palpated on examination or when routine abdominal radiographs are performed. Treatment depends on the location and type of tumor. Many abdominal masses are malignant and most are attached to an organ. If your vet finds or suspects an abdominal tumor, often the first step is to do abdominal radiographs and/or abdominal ultrasound. Chest radiographs are done to check for metastasis in the lungs. Your vet might recommend referral to a veterinary specialist for advanced diagnostics and expert recommendations. Some abdominal tumors can be biopsied to determine malignancy. They are usually surgically removed if this is possible.

Canine Lymphoma

Lymphoma is not actually a tumor; it is a cancer of the lymphatic system. However, the first sign of lymphoma is usually an enlargement of the lymph nodes. This inflammation may look like tumors to you because the lymph nodes become very large, round, and lumpy. Pet owners most often notice lumps in the neck area, but they may also be found in the axillary area (armpits), the inguinal area (lower abdomen near thighs), and the back of the knees. Lymphoma is often diagnosed with FNA or biopsy, but the lymph nodes are not typically removed. Chemotherapy is the most common treatment for lymphoma.