What do cysts on dogs look like

Finding a lump on your dog can be unnerving. Thankfully, if it is a sebaceous cyst, dog parents can rest a bit easier knowing this type of mass, while sometimes annoying or unsightly, is benign. Integrative veterinarian Dr. Julie Buzby explains what a sebaceous cyst on a dog looks like, why one might occur, and details the diagnostic and treatment process.

Many of our senior pups are no strangers to lumps and bumps. Sometimes a new growth can appear seemingly overnight. Other masses may be slow growing. Whether you just noticed it or know it has been lurking for awhile, lumps can be concerning. Understandably, you may worry what this bump could mean for your canine companion. But the good news is that not all masses are the cancerous kind!

One of the more common types of growths are skin cysts. A cyst is usually a small, sac-like nodule located on or in the skin. The hollow space within cysts may contain fluid or waxy debris depending on the type of cyst. Many of these cysts, like sebaceous cysts, are noncancerous but can be prone to secondary bacterial infections.

What are sebaceous cysts in dogs?

Cysts often occur inside hair follicles, which are tiny openings that provide a base for hair or fur to attach. Cysts involving follicles also are known as follicular cysts, and there are several variations. Follicular cysts are characterized by their contents (such as keratin) and by the origination of the cells that make up the lining of the cyst. Most cysts come from glandular tissue like sweat glands. However, in the case of sebaceous cysts, they originate from the sebaceous glands (i.e. oil glands) that adjoin the hair follicles.

Compared to other follicular cysts, sebaceous cysts are one of the most common skin growths in dogs. Sebaceous cysts develop when sebaceous glands release an oily secretion called sebum, which then enters a nearby hair follicle. Usually, sebum plays a role in maintaining skin health. But if sebum becomes trapped or the body releases too much sebum, a cyst can form. The picture below shows a sebaceous cyst on a dog.

What causes a sebaceous cyst?

Although the true cause of sebaceous cysts in dogs isn’t completely understood, it is thought that cysts can result from the blockage of a follicle or skin pore. This is because obstructions can lead to the accumulation of dead skin cells and secreted glandular materials inside follicles. The following factors may increase the risk of cyst formation:

• Trauma or injuries to the skin 
• UV ray damage from the sunlight
• Inflammation or infection
• Scar tissue accumulation
• Hair follicle inactivity in hairless breeds

What does a sebaceous cyst look like on a dog?

In most cases, a sebaceous cyst is characterized by a small, raised bump that appears on or beneath a dog’s skin. Cysts are usually solitary lesions but it’s possible for dogs to have multiple cysts scattered across their body. The average size of a sebaceous cyst can vary anywhere from one-quarter of an inch to two inches wide. Cysts are often smooth in appearance with a white or bluish color, but they can sometimes have hair coming out of them because of neighboring hair follicles.

Below you’ll see a picture of a sebaceous cyst on a dog. Throughout this article, you’ll see more pictures of sebaceous cysts on dogs to illustrate the variation in what they may look like.

Because sebaceous cysts can rupture, you might not notice they are there until you see bleeding or discharge coming from the site. Sebaceous cysts can excrete discharge that is light grey or white in color. Sometimes, the cyst’s debris can have a cottage-cheese (i.e. caseous) appearance. There usually isn’t a bad smell associated with a ruptured cyst unless it has become infected by bacteria.

Why can sebaceous cysts become a problem?

Sometimes sebaceous cysts can be very “quiet” in nature. This means they are nothing more than a slight blemish on your dog’s skin. However, if the dog scratches the cyst or the groomer accidentally catches it with the clippers, bacteria and yeast on the skin can contaminate the site and cause infection. The area around an infected cyst may be red, inflamed, or have an unpleasant odor. If you notice any of these signs, your dog needs veterinary attention.

Also, as mentioned above, it is possible for sebaceous cysts to burst when the cyst becomes too full or does not have enough room to grow. Immediately after rupturing, you may notice a lot of discharge and/or bleeding from the site. It may also be painful or uncomfortable for your poor pup. You should make an appointment with your vet to address a ruptured or bleeding cyst as soon as you can. This is especially true if your dog is licking or biting the area or you notice signs your dog is in pain.

Where do sebaceous cysts tend to occur?

Sebaceous cysts can appear anywhere on your dog’s body. In very young dogs, sebaceous cysts will usually appear on the top of their heads. For dogs of all ages, the most common locations are the head, neck, chest, and upper limbs. Also, dogs can get a similar type of lump on the margin of their eyelid. These occur when secretions from the meibomian gland, a modified sebaceous gland that produces the oil portion of the tear film, build up and form a cyst. The picture below shows how a sebaceous cyst can occur on a dog’s eyelid margins.

Dogs also can develop sebaceous cysts at pressure points like the elbows. A variety of types of cysts, including sebaceous cysts, may occur on a dog’s paws. This can make walking uncomfortable. Additionally, some dogs may develop a condition called stud tail. It occurs when oily secretions build up from the supracaudal gland. This specialized gland is found at the base of the tail and is composed of sebaceous glands and some sweat glands. While not a true cyst, cases of stud tail do involve over production of sebum and the potential for infection of the gland.

Which dogs tend to get them?

Sebaceous cysts can affect both males and females equally. They tend to affect middle-aged dogs more than other age groups. Some breeds have a genetic predisposition for developing sebaceous cysts. These include:

• Boxers
• Shih Tzus
• Basset Hounds
• Schnauzers
• Yorkshire Terriers
• Doberman Pinschers

Because follicular inactivity can increase the risk of cyst formation, this means hairless breeds like the Chinese Crested and the Xoloitzcuintli (i.e. Mexican Hairless Dog) can develop multiple cysts.

How will my vet diagnose a sebaceous cyst?

It is important to remember that many lumps and bumps can look the same. Most skin cysts will be observed on the surface of the skin, visible to the naked eye. But just because you think it looks like a sebaceous cyst doesn’t always mean that it is a sebaceous cyst.

You should always inform your vet about any new lumps you find. Doing so means your vet can perform additional testing to determine the type of mass. This can put your mind at ease. It can also help prevent a situation where something you think is a sebaceous cyst is actually a cancerous mass that needs to be addressed sooner rather than later.

Fine needle aspirate

In some cases, your veterinarian may recommend a fine needle aspiration (FNA) test. For this, the vet will use a needle to perforate the mass and collect the material and/or cells within. FNA testing is useful for a wide variety of skin tumors, such as mast cell tumors, or subcutaneous (i.e. under the skin) tumors, such as lipomas in dogs. However, sometimes in the case of smaller or firm skin cysts (like sebaceous cysts), the aspirate may only yield normal skin cells, inflammatory cells, or cellular debris.

Biopsy

If FNA testing is inconclusive and the vet is concerned the mass could be something dangerous, he or she may recommend a biopsy. This is because biopsies, while more invasive, tend to provide more accurate results. Rather than pulling cells or debris from the mass like an FNA, a biopsy involves removing a small piece of tissue. The vet will then submit the tissue to a pathologist for further analysis.

Since some sebaceous cysts are very small, a cyst biopsy may mean surgically removing the cyst for further evaluation. As an added bonus, if the pathologist confirms the vet removed the entire cyst, the biopsy may be curative!

Dealing with diagnostic surprises

Pathologists may use the more correct term “keratin inclusion cyst,” “follicular cyst,” or “epidermal inclusion cyst” to describe what is commonly known as a sebaceous cyst. This is because true sebaceous cysts (i.e. those filled with sebum only) are relatively rare in veterinary medicine. Instead, the so called “sebaceous cysts” are also filled with keratin, which is the white or chunky part of the contents.

So don’t be surprised or concerned if you were expecting to see “sebaceous cyst” as the diagnosis and see one of these other terms instead. They are, for all practical purposes, the same thing.

Also, keep in mind that different types of lumps and bumps can look very similar. As a result, your dog’s FNA or biopsy may occasionally come back with an unexpected result. Benign tumors like hamartomas and sebaceous adenomas can look like sebaceous cysts but still carry a good prognosis. On the other hand, some cancerous bumps like squamous cell carcinoma may also mimic a sebaceous cyst. But a biopsy will reveal their true identity. No matter the diagnosis, your vet will be there to help you figure out the next steps—even if the plan looks different than you thought it would.

What is the treatment for sebaceous cysts?

Once your vet confirms the new bump is indeed a sebaceous cyst, he or she will go through the treatment options with you. Sometimes, your vet can manage small but inflamed sebaceous cysts with antibiotics, anti-inflammatories, and topical treatments.

The Canadian Veterinary Journal published a case study entitled Successful control of disseminated follicular cysts in a dog with low dose isotretinoin. In it, veterinarians used oral isotretinoin (a vitamin A derivative) in a dog with numerous cysts. The study showed that the isotretinoin helped resolve the cysts when it was combined with a short course of oral antibiotic. Perhaps this could become a more widely available option at some point.

If you and your vet address the underlying cause for a sebaceous cyst (such as treating an infection, for example), it can sometimes become smaller or even disappear altogether. Also, cysts that develop due to skin injuries or trauma may resolve over time. So some veterinarians might recommend to simply monitor skin cysts for any changes. This is especially the case if the cysts aren’t problematic for you and your canine companion. 

If the sebaceous cyst is breaking open, bleeding, becoming infected, or won’t go away, your veterinarian may recommend surgical removal. Sebaceous cyst removal via surgery is the most effective type of treatment. This is especially the case if the cyst has ruptured or has become infected. The cyst can be cut out using an incision or removed via a surgical laser. Most veterinary dermatology specialists are able to remove cysts with a laser. This technique is especially useful if there are multiple cysts, which is common with hairless dog breeds.

Generally, once a cyst is removed, it won’t come back again. However, this doesn’t mean the dog won’t form sebaceous cysts in other areas.

At home treatment for sebaceous cysts on dogs

Treating sebaceous cysts is primarily the job of your veterinarian. Unfortunately, most at-home treatments will not resolve a sebaceous cyst entirely. And there aren’t many treatments that will help to prevent sebaceous cysts from occurring. However, there are some things you can do for your pup in the event of a cyst rupture. Plus, general skin care can make a huge difference in the life of your furry (or hairless) friend.

Resist the urge to squeeze the cyst

Although it may be satisfying to squeeze a pustule or blackhead (a la Dr. Pimple Popper), it is important to avoid manually expressing sebaceous cysts. Not only can this introduce bacteria into the cyst when it ruptures, but it can also cause cyst contents to move deeper into the affected area. In some cases, this can trigger an allergic reaction. This happens when the immune system treats the cyst contents like a new infection or a foreign body.

First-aid for a ruptured cyst

Unfortunately, large sebaceous cysts can unintentionally rupture, releasing their contents. These situations can be very messy because cysts can sometimes bleed. It can also be really scary when you’ve never seen it happen before! This is where having a dog first aid kit comes in handy.

If the cyst is bleeding, you can use sterile gauze or non-stick pads to apply firm but gentle pressure. Sometimes the site will be dirty (for example, if the rupture happened out in the yard). In that case, clean it with warm water and gentle soap. Diluted chlorhexidine or iodine can be great disinfectants. However, avoid using hydrogen peroxide as it is harmful to new, healthy cells.

Consider using a bandage or a loose-fitting shirt (depending on the cyst’s location) as a covering until you can get to your vet. Putting an Elizabethan collar (E collar) on your dog in the meantime can also prevent your pup from licking the site.

Take steps for good skin health

As mentioned, promoting healthy skin is great for all dogs, including those who are prone to sebaceous cysts. And good skin health starts with good nutrition. All dogs should eat a properly balanced diet. If the diet is a home-cooked meal instead of a commercial diet, ensure the recipe has been formulated by a board certified veterinary nutritionist. This is because diets with missing ingredients can lead to skin problems and other disorders.

Sometimes you can purchase (or make) diets created specifically for skin health. They tend to contain extra vitamin E and omega-3 fatty acids for dogs. It also may be a good idea to ask your vet if a fish oil supplement (an excellent source of omega-3s) would be beneficial for your dog.

Additionally, some dogs may have excessively oily skin. This is especially true for hairless dog breeds and for dogs who have a condition called seborrhea oleosa. This is a skin disorder where sebaceous glands release too much sebum. Shampoos and medicated wipes that contain ingredients like benzoyl peroxide can remove excess oil. Plus, they can promote healthy skin cells by removing layers of dead cells. Your veterinarian may recommend bathing your dog with a benzoyl peroxide shampoo once a week or every other week.

Be proactive about skin masses

One of the biggest pieces of advice I can give regarding skin tumors is not to take a “wait and see” approach. Yes, sebaceous cysts on dogs are fairly common. But that doesn’t mean that every skin mass that pops up is a sebaceous cyst, even if it looks like one to you. It is much better to make an appointment with your vet now and find out it was just a sebaceous cyst than it is to regret waiting because the mass ended up being something else.

Also, your vet probably only gets to examine your dog once or twice a year. So don’t rely on him or her to be the only way to find new masses. Instead, be proactive with your canine companion’s health. Check his or her skin at least once a week to see if there are any new lumps or bumps. This can be part of your tip-to-tail dog wellness scan.

Make notes about the location of the lump and its initial appearance. Then make an appointment with your veterinarian so he or she can evaluate the mass. This approach will give you the best chances of either catching problems early or feeling confident that the mass isn’t a problem.

Has your dog had sebaceous cysts?

Please share your experience in the comments.