10 Types of Cysts on Dogs you Should Watch out For

Dog at the Vet

Cysts are non-cancerous sac-like structures filled with semi-solid, liquid, or gaseous materials that look like blisters. They vary in size from microscopic to extremely large. Large cysts are capable of displacing internal body organs. The majority of the cysts are non-cancerous, but some can be precancerous or cancerous. A cyst is formed from a separate tissue with a distinct membrane that is not part of the normal tissue. The outer part of a cyst is known as a cyst wall. An infected cyst is usually filled with pus that turns into an abscess.

Causes of Cysts in dogs

Cysts are common in dogs, and they can occur anywhere on the surface of the body. They are mostly caused by piercings, infections, and clogged sebaceous glands. Other common causes of cysts are; tumors, parasites, injuries, genetic conditions, defects in the cells, and blockage of ducts in the body that causes fluids to build up, and chronic inflammatory conditions. Cysts are painless unless they are infected and inflamed, which causes them to rapture.

Signs of cyst on your dog

The type of cyst a dog has will also determine the signs and symptoms. In most cases, the first sign you will notice is an abnormal lump, especially when the cyst forms below the skin. It may be difficult to notice internal cysts because they do not cause symptoms. According to MedicalNewsToday, the only way they can be seen is to do a CT scan, an MRI, or an ultrasound. If a cyst develops in the brain, it can cause migraines, among other symptoms. Cysts which grow on the breasts are also painful. In dogs, the ten types of cysts that you should watch out for are;

1. Follicular cysts

Follicular cysts develop as nodules or large bumps on a dog’s skin. They are the most common type of skin masses or bumps that a dog can have. Follicular cysts start to form on the hair follicle, and that is where they get their name. They start out as a thick yellow, a white or brown substance that becomes itchy and painful as it develops. In most cases, only one follicular cyst is visible, but there can be many simultaneously, although this is rare. Other common names of follicular cysts are hybrid, isthmus, epidermal and metrical cysts.

  • Diagnosis- can only be diagnosed by a veterinarian. They will take skin samples and place them under a microscope. The vet may use a fine needle aspirate to take the skin sample. If the follicular cyst is painful and still growing, the vet may decide to remove the entire mass through a biopsy surgery.
  • Treatment: Follicular cysts develop only on the skin and rarely spread to other parts of the body. At times, they become infected, and if this happens, your vet will take skin samples and perform a skin culture which will help him determine the appropriate antibiotic to administer. Antibiotics are drugs that fight bacteria. If the follicular cyst is painful, a biopsy surgery is good for treatment. Once the cyst has been removed, it is impossible to regrow.

2. Sebaceous cysts

They are bumps or swellings that develop beneath the skin of a dog. Sebaceous cysts form when a hair follicle or the skin pore is clogged by dirt, debris, or scar tissue. Sebaceous cysts also form when sebum blocks the skin pores and hair follicles. Sebum is a substance that keeps skin shiny and healthy. These cysts develop as large pimples. When the dog can no longer excrete oil from the clogged pore through sweat, it continues to grow and become large and forms into a cyst. Although sebaceous cysts are harmless, they can be infectious if not treated. One way of treating them at home is to use prescribed medication from the vet.

  • Diagnosis- According to EveryCreatureCounts, sebaceous cysts are diagnosed through physical examination by your vet. The vet will analyze your dog’s skin where the lump has developed. If the lump feels abnormal, the vet may take a skin sample and test it at the clinic. The sample will determine if the lump is a tumor or a sebaceous cyst that you can treat easily. If the vet is unsure, they might consider doing a biopsy and taking out a small piece of the lump for a definitive diagnosis.
  • Treatment- sebaceous cysts are treated using antibiotics and anti-inflammatory medications.

3. Dermoid cysts

They are typical tissues found mostly around the eyes. Dermoid cysts tend to grow in abnormal places. They tend to cause discomfort and irritation when they grow near the eyes. Dermoid cysts are found in specific breeds of dogs, and they can start to develop as early as birth. One of the signs of ocular Dermoid is discharge and abnormal growth. Even if the cysts are irritating your dog, it is harmless, and there are no health risks associated with them. Ocular dermoids are normal tissues that grow in abnormal places. They can grow on the cornea or the eyelid. Common symptoms of ocular Dermoid are hair growing towards your dog’s eye, discharge, irritation, growth on the eyelid, and cloudiness of the eye.

  • Diagnosis- if you notice any issue with your dog’s eyes like hair growth, discharge, cloudiness, and irritation, it is good to visit the vet for diagnosis to determine whether it is an ocular Dermoid. If you have adopted the dog and are unsure about the breed, please mention it to your vet, as it will help with the diagnosis. The diagnosis will determine if it is growth or lesions.
  • Treatment- the only treatment for ocular dermoids is noninvasive surgery done to remove the growths.

4. False cysts

To understand what a false cyst is, we need to know what a cyst is. Cysts are non-cancerous sac-like structures filled with semi-solid, liquid, or gaseous materials that look like blisters. False cysts do not have an interior lining, and they are not filled with any substance. They occur due to injuries of the surrounding tissues.

As the tissues of the injured cells deteriorate, they tend to liquefy, which creates bumps as a response to the immune system. False cysts normally occur around the legs of your dog, and they can be caused by injuries or a reaction to an injection. Treatment- According to VcaHospitals, false cysts can heal on their own without medications. Since no liquid is formed, any additional fluid excreted is reabsorbed into the body. This makes the false cyst decrease in size and dies slowly. In cases of severe injury, the cyst may need to drain.

If the cyst is not reducing in size, your vet may create an incision to drain the fluid and reduce the pressure. They can also use a small gauge needle to withdraw fluid from the infected area. Warm compresses and gentle massages should be applied to the infected area to help reabsorption of the fluid and heal the surrounding tissues.

5. Epidermoid cysts

Epidermoid cysts are small non-cancerous bumps that form underneath the skin. They appear anywhere on the skin but mostly on the neck, face, and trunk. Epidermoid cysts are painless and slow-growing, making it hard to detect them. The skin, also called the epidermis, is made up of a thin layer and cells that are constantly shed by the body. Epidermoid cysts are formed when the skin cells are not shed off and move deeper into the skin. They can also form as a result of an infection or an injury.

If the cyst is painful or has ruptured, the vet can remove it. Many people confuse epidermoid cysts with sebaceous cysts, but they are different. Sebaceous cysts form in hair follicles that secrete the oily substance that lubricates hair. According to Bmcvetres, symptoms of epidermoid cysts are redness, swelling, and tenderness in the affected area, a small, round bump under the skin, and a thick, yellow, smelly material that drains from the cyst.

6. True cysts

True cysts form in sweat glands, and they have a secretory lining on the inner surface that produces secretions. They form when the sweat duct is blocked by dirt, debris, or a scared tissue. To prevent the reoccurrence of the cyst, the secretory lining needs to be removed through surgery.

7. Bone cysts

Bone cysts are non-cancerous radiolucent cavities that form in the long bones of dogs. They can also be found in flat bones such as mandibles and ribs. There are four types of bone cysts; aneurysmal, subchondral, monostotic, and polyostotic. Aneurysmal bone cysts are rare and occur in specific dog breeds. Breeds that suffer from bone cysts are Doberman pinscher, Saluki, German shepherd, Great Dane, and Weimaraner.

The clinical signs of bone cysts are swelling, pain, stiffness in the joints, and acute swelling caused by pathologic fracture. Diagnosis- According to ScienceDirect, bone cysts can only be detected by surveyed radiographs and histopathology. Surveyed radiographs can show the pathologic fractures that cause acute swelling, while histopathology is done on aneurysmal cysts filled with blood and lined with connective tissues. Treatment-bone cysts are treated by filing the pathologic fractures by fracture fixation, debridement of the cyst wall, and cancellous graft. If the bone cyst is found in flat bones, then a cyst resection of the lesion can be done.

8. Histiocytoma cysts

Histiocytoma is a non-cancerous skin cyst that forms on the skin of young dogs. Young dogs, especially those under the age of three, are likely to develop histiocytoma cysts on the face and extremities. Histiocytoma forms as an abnormal extension of histiocytes on the skin. Histiocytes are the skin’s immune system that acts as a barrier that prevents bacteria from attacking the skin.

Histiocytoma cysts form when the histiocytes are disarrayed, leaving them open to bacterial infection and injuries. As much as they are non-cancerous, many dog owners find them unpleasant to look at. According to Petmd, the clinical signs and symptoms are small solitary hairless lumps on the neck, head, ears, and limbs. In rare cases, the dog can have several masses at once. The lumps are small in size, about 2.5cm in length, and may appear as reddish on the skin’s surface.

  • Diagnosis- cytology can be used in the initial diagnosis of histiocytoma cysts, although the results might not be conclusive. Histopathology can be used to give definitive results. These cysts are common in Labrador retrievers, boxers, pit bull terriers, American Staffordshire Terriers, Boston Terriers, and Scottish terriers.
  • Treatment- histiocytoma cysts are highly treatable. Once they form, they regress slowly within a few months, and they may reach a point where they outgrow the normal standard of a tumor. If it gets to this point, the cyst needs to be removed as soon as possible before it can spread to other parts. The treatment will depend on the cyst’s appearance, size, inflammation, and cytological appearance. After assessing all of the above and the dog’s history of past skin infections, the vet will then prescribe the recommended medication.

9. Mucous cysts

Mucous cysts are fluid-filled swellings that occur on the lips or the mouth. They are formed when the salivary glands found in the mouth become plugged with mucus. Infections cause mucous cysts in the oral cavity from salivary gland disruption and lip biting.

10. Papilloma cysts

They are more common in dogs than in cats. Papillomas are sometimes called warts, and they appear when the skin is infected by papillomavirus, which inserts their genetic information on the skin cell, interrupting the normal process of skin division. They tend to disappear after a while once a dog gains immunity against them. If they don’t disappear, they can be removed through surgery before they become inflamed and infected, making it harder to treat them.


Cysts are common infections in dogs that are treatable through surgery. Laser treatment may be used for sweat gland cysts. It is important to prevent your pet from biting, rubbing, and scratching the infected area after surgery.

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