My Cat's Cyst Keeps Filling Up, What's Wrong? (Vet Answer)

Over their lifetime, our cats can develop all sorts of weird and wonderful lumps, bumps, swellings, and more. One of the least worrying lumps you might encounter is a cyst, although it’s hard not to worry when anything unusual starts growing out of your pet!

Cysts are fluid-filled pockets on or under the skin, and there are several types to be aware of. The most common type of cyst we see in cats is caused by a blocked or damaged sweat gland, and apart from being a bit unsightly, they are completely harmless. If these cysts are drained or ruptured, you might be surprised to find that they refill, virtually overnight! Don’t panic, as this is completely normal.

If you’ve noticed a soft lump appear on your cat’s skin, the first thing you need to do is get your cat and their cyst checked out by your vet. Although most cysts are harmless, there is always a risk of secondary infection, and over time, a once-benign cyst could become cancerous.

Let’s take a closer look at feline cysts and why they keep filling up.

What Are Feline Cysts?

There are a few different types of cysts that could appear on your cat, but the one that is most likely to keep filling up is a true cyst. This means that the cyst is lined with a membrane that secretes a watery fluid, usually caused by a blocked sweat gland. We mostly see them on the face, head, and neck. They are generally painless, harmless, and will not become cancerous.

True cysts are often mistaken for sebaceous cysts, which occur commonly in dogs but rarely in cats. Sebaceous cysts are normally associated with hair follicles and are filled with an oily substance called sebum, a natural skin moisturizer.

Follicular cysts, also known as feline acne, are the result of blocked or congested hair follicles and are very similar to our blocked pores or blackheads. They often appear as small, black crusting lesions on the chin, but they can become inflamed and (rarely) turn into benign tumors.

Feline ceruminous cystomatosis is believed to be a congenital malformation seen rarely in cats. It results in the growth of multiple apocrine or ceruminous cysts on the inner surface of the ear. Although these cysts are benign, they can grow in size and number to obstruct the ear canal. When this happens, surgery is recommended and is usually successful.

Why Does My Cat’s Cyst Keep Filling Up?

The membranous lining of true cysts naturally produces fluid, so it makes sense that they will continue to do so, even after the cyst has been drained. Often, by draining the cyst, we can end up stimulating those cells to produce more fluid, and over time, the cyst may get bigger. The more we drain it, the bigger it gets. Another potential risk of draining these cysts is introducing infection.

However, sometimes we need to drain a cyst because of its location or size, and other times it may be damaged or ruptured on its own.

Although some cat owners learn how to drain these cysts at home, it is not something we would generally recommend due to the risk of introducing infection or encouraging further enlargement of the cyst. You can talk to your vet about how best to manage your cat’s cyst, depending on its location and size.

If the cyst continues to cause problems, your vet may recommend surgical removal. To be successful, the entire cyst must be removed to ensure that the fluid-secreting membrane has been eliminated; otherwise, the cyst will likely reform.

When Is a Cyst Not a Cyst?

We know that there are several different types of cysts, but there are also several other conditions that might look like cysts. That’s why it’s important to get your cat’s cysts checked by a vet, because it may not be a cyst at all. Here are some conditions that may masquerade as cysts:

Abscess

If not the most common reason a cat ends up at the vet, it has to be one of the most common, particularly for cats that venture outside. When a cat’s skin is punctured by a tooth or claw, usually belonging to another cat, it’s like having an infection injected into the skin. After a few days of brewing, a pocket of pus begins to form, also known as an abscess.

Abscesses on the face are often caused by tooth infections. They often look like a harmless cyst, but unlike a cyst, it will be warm and painful.

Tumors

Certain types of tumors can be mistaken for cysts (and vice versa).

Lipomas are benign fatty lumps that usually feel soft and mobile under the skin. Like a cyst, they should not be painful, but they can grow quite large and often need to be removed surgically.

Squamous cell carcinoma is the most common type of skin cancer in cats, and in the early stages, it can sometimes look like a cyst or multiple cysts. This malignant cancer occurs most commonly in white/non-pigmented parts of the face, like the ears, nose, mouth, and around the eyes. Early removal of this type of skin cancer can be quite successful but difficult to treat once it grows into deeper structures.

Aural Hematoma

Aural hematoma is a swelling of the ear caused by trauma, usually from scratching, and commonly associated with ear infection. These are much more common in dogs but do also affect cats.

Damage to the connective tissue of the ear results in serosanguinous (blood and serum) fluid building up in a pocket between the ear cartilage and the skin. They can be uncomfortable and sometimes quite painful. In cats, aural hematomas will sometimes resolve with conservative treatment (draining the fluid and treating the underlying infection), but they occasionally need surgery to stop the hematoma from refilling.

False Cysts

These are simple, fluid-filled swellings, a bit like a hematoma, but can be found anywhere on the body. They are usually the result of some sort of trauma or can appear at the site of an injection. False cysts rarely require treatment and resolve on their own.

Conclusion

Cats can have different types of cysts, most of which are quite harmless. Because a true cyst is lined with cells that produce fluid, they tend to refill whenever they are drained or ruptured. Regular draining of these cysts may encourage increased fluid production, causing the cyst to grow larger. It also increases the risk of infection, and we generally advise against draining these cysts unless your veterinarian feels it is necessary.

If you think your cat might have a cyst, you should always have your vet take a look. While most feline cysts are benign, there are several conditions that look like cysts that can be harmful.

Featured Image Credit: Irina Vasilevskaia, Shutterstock