Cysts are closed capsule or sac-like structures, typically containing a liquid, semisolid, or gaseous material, much like a blister.

Cysts vary in size from microscopic to very large. Very large cysts can displace internal organs.

A cyst is not a normal part of the tissue where it occurs. It has a distinct membrane and is separate from nearby tissue. The outer, or capsular, portion of a cyst is known as the cyst wall.

If the sac has filled with pus, the cyst is infected and will turn into what doctors call an abscess.

They are usually benign, but some cysts can be cancerous or precancerous.

This article looks at the different types of cysts, their causes and symptoms, and some treatment options.

A collage depicting different types of cysts.Share on Pinterest
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Some common types of cyst include:

Acne cysts

Cystic acne, or nodulocystic acne, is a severe type of acne in which the skin’s pores become blocked, leading to infection and inflammation.

Arachnoid cysts

The National Institute of Neurological Disorders and Stroke notes that arachnoid cysts develop between the arachnoid membrane and the brain or spinal cord. These cysts contain cerebrospinal fluid.

Arachnoid cysts may affect newborn babies. Doctors call these primary arachnoid cysts.

The arachnoid membrane covers the brain. During fetal development, it doubles up or splits to form an abnormal pocket of cerebrospinal fluid. In some cases, a doctor may need to drain the cyst.

Secondary arachnoid cysts develop as a result of head injury, tumors, or meningitis.

Baker’s cysts

Baker’s cysts are also known as popliteal cysts.

Some do not cause any symptoms. However, a person with a Baker’s cyst can experience:

  • knee pain
  • a lump behind the knee
  • a feeling of fullness behind the knee
  • swelling in the knee and lower leg
  • stiffness or tightness located at the back of the knee

Baker’s cysts usually develop due to a problem with the knee joint, such as arthritis or a cartilage tear.

Bartholin’s cysts

Bartholin’s cysts can occur if the ducts of the Bartholin gland, which are inside the vagina, become blocked.

A doctor may recommend surgery or prescription antibiotics as treatment.

Breast cysts

Breast cysts are common and may be painful.

In females, these cysts can develop or change in size throughout the menstrual cycle, and they often disappear on their own. However, a doctor can drain the fluid if they are causing discomfort.

According to the American Cancer Society, simple cysts do not increase the risk of breast cancer. That said, there is a small chance that complex cysts may contain cancer or increase a person’s risk of cancer later on, depending on the results of a biopsy.

Read more about breast lumps here.

Chalazion cysts

Very small eyelid glands, known as meibomian glands, make a lubricant that comes out of tiny openings in the edges of the eyelids. Cysts can form here if the ducts are blocked. These are known as chalazion cysts.

Colloid cysts

Colloid cysts develop in the brain and contain gelatinous material.

Treatment depends on whether the cyst is causing symptoms or a buildup of fluid in the brain. In these cases, a doctor may recommend surgery to remove the cyst or aspiration (draining).

Dentigerous cysts

Dentigerous cysts surround the crown of an unerupted tooth.

Dermoid cysts

Dermoid cysts comprise mature skin, hair follicles, sweat glands, and clumps of long hair, as well as fat, bone, cartilage, and thyroid tissue.

They can form anywhere on the body.

Epidermoid cyst

A 2021 article notes that people may also refer to these as “sebaceous cysts.” However, these cysts do not involve the sebaceous gland, and healthcare professionals call them epidermoid cysts instead.

These cysts occur on the skin of the face, back, scalp, or scrotum and contain keratin material.

Epididymal cysts

Epididymal cysts, or spermatoceles, form in the vessels attached to the testes.

They are benign and contain a fluid that is white and cloudy. They also contain sperm.

They are not a serious medical issue and rarely need treatment. However, treatment may be necessary if they cause pain or become too large.

Read more about testicle lumps here.

Ganglion cysts

Ganglion cysts are small, benign cysts that form on or near a joint or covering of a tendon.

They usually develop on the wrist and hand but can also appear on the foot, ankle, or knee.

Hydatid cysts

Hydatid cysts develop due to a relatively small tapeworm. These cysts form in the lungs or liver.

Treatment options include surgery and medication.

Kidney cysts

There are several types of kidney cysts, or renal cysts. They are usually harmless.

Solitary cysts contain fluids, sometimes including blood. Some are present at birth, while tubular blockages cause others.

People with renal vascular diseases may have cysts that formed due to dilatation of the blood vessels.

Ovarian cysts

Ovarian cysts are common in females who have regular periods. They form during ovulation.

The majority of ovarian cysts are benign and cause no symptoms. However, some can become so large that the abdomen protrudes.

Polycystic ovary syndrome refers to when the ovaries develop many small cysts.

Pancreatic cysts

Health professionals may refer to them as “pseudocysts” because they do not contain the types of cells present in true cysts.

They occur when the cells of the pancreas are injured or inflamed. They can also occur when pancreatic enzymes leak and damage the tissue of the pancreas.

Periapical cysts

Periapical cysts, also known as radicular cysts, are the most common type of odontogenic cysts, which are related to the formation and development of teeth.

These cysts usually develop due to inflammation of the pulp, pulp death, or tooth decay.

Pilar cysts

Pilar cysts are also known as trichilemmal cysts. They are fluid-filled cysts that form from a hair follicle and usually develop in the scalp.

Pilonidal cysts

Pilonidal cysts form in the skin near the tailbone or lower back, and they sometimes contain ingrown hair.

These cysts can grow in clusters, which sometimes creates a hole or cavity in the skin.

Pineal gland cysts

These are benign cysts that form in the pineal gland in the brain.

According to a review from 2020, pineal gland cysts are common.

Tarlov cysts

Tarlov cysts — also known as perineural, perineurial, or sacral nerve root cysts — occur at the base of the spine and are filled with cerebrospinal fluid.

Vocal fold cysts

There are two types of vocal fold cysts: mucus retention cysts and epidermoid cysts.

Vocal fold cysts can interfere with the quality of a person’s speech, sometimes causing their vocal cords to produce:

  • multiple tones simultaneously, known as diplophonia
  • breathy speech, or dysphonia
  • hoarseness

The signs and symptoms will vary widely depending on what type of cyst it is. In many cases, a person first becomes aware of an abnormal lump, particularly when the cyst is just beneath the skin.

Many internal cysts, such as those that occur in the kidneys or the liver, may not cause any symptoms at all. A person may not notice them until an imaging scan — such as an MRI, CT, or ultrasound scan — detects them.

It is unusual for some cysts, such as skin cysts, to cause pain unless they rupture, become infected, or are inflamed. However, breast cysts can cause pain.

A person may also experience headaches and other symptoms if a cyst develops on the brain.

Cysts are common and can occur anywhere on the body. They can be a result of infection, clogged sebaceous glands, or piercings.

Some other causes of cysts include:

  • tumors
  • genetic conditions
  • a fault in an organ of a developing embryo
  • a defect in the cells
  • chronic inflammatory conditions
  • blockages of ducts in the body that cause fluids to build up
  • a parasite
  • an injury that breaks a vessel

Cysts are usually benign and develop due to blockages in the body’s natural drainage systems.

However, some cysts may be tumors that form inside tumors. These can be malignant, or cancerous.

Cysts are not the same as tumors.

Learn about tumors versus cysts here.

The treatment options for a cyst will depend on a range of factors, including the type of cyst, where it is, its size, and the degree of discomfort it is causing.

For very large cysts that are causing symptoms, a doctor may recommend surgical removal.

Sometimes, a doctor can drain, or aspirate, the cyst by inserting a needle or catheter into the cavity. If the cyst is not easily accessible, they may use radiologic imaging to accurately guide the needle or catheter.

A healthcare professional may examine the removed liquid under a microscope to determine whether or not any cancerous cells are present. If they suspect that the cyst is cancerous, they may suggest surgical removal, order a biopsy of the cyst wall, or both.

Some cysts develop as a result of a chronic or underlying medical condition, as may be the case with fibrocystic breast disease or polycystic ovary syndrome. In such cases, the focus of the treatment will be on the medical condition itself, not the cyst.

Although cysts and boils can appear similar in appearance, their causes and treatment options are different.

A cyst is a closed sac that consists of liquid, gaseous, or semisolid material.

A boil is a lump that has filled with pus and develops around hair follicles. They usually occur as a result of a bacterial infection.

Learn more about cysts versus boils here.

Cysts are abnormal, fluid-filled sacs that can develop in tissues in any part of the body. They are relatively common, and there are many different types.

Infections, tumors, parasites, and injuries can cause cysts. They are usually noncancerous.

If a person is worried about a cyst or has noticed a new lump, they should see a doctor for an accurate diagnosis and treatment, if necessary.