Cysts are closed capsule or sac-like structures, typically filled with 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. The majority are benign, but some cysts can be cancerous or precancerous.

A cyst is not a normal part of the tissue where it is located. It has a distinct membrane and is separated from nearby tissue. The outer (capsular) portion of a cyst is called the cyst wall.

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

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

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

Some other common 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

In most cases, it is unusual for cysts to cause pain unless they rupture, become infected, or are inflamed.

Most cysts are 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 vs. cysts here.

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. They may go unnoticed until an imaging scan — such as an MRI, CT, or ultrasound scan — detects them.

If a cyst develops on the brain, it can cause headaches and other symptoms. Breast cysts can also cause pain.

Some of the most 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

Arachnoid cysts may affect newborn babies.

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.

Baker’s cysts

Baker’s cysts are also called popliteal cysts. A person with a Baker’s cyst often experiences a bulge and a feeling of tightness behind the knee. The pain may worsen when extending the knee or during physical activity.

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 situated 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, but they do not usually require any treatment.

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 might 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, called 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. Doctors often recommend surgical removal as treatment.

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.

Epididymal cysts

Epididymal cysts, or spermatoceles, form in the vessels attached to the testes. This type of cyst is common and does not typically impair fertility or require treatment. If it causes discomfort, however, a doctor may suggest surgery.

Read more about testicle lumps here.

Ganglion cysts

Ganglion cysts are small, harmless cysts that form on or near a joint or covering of a tendon. They usually develop on the wrist but can also appear on the hand, 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 cyst, or renal cyst. 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 the 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

Most health professionals do not consider pancreatic cysts as true cysts. Instead, they refer to them as “pseudocysts,” as they do not contain the types of cell present in true cysts.

They can include cells normally present in other organs, such as the stomach or intestines.

Periapical cysts

Periapical cysts, also known as radicular cysts, are the most common type of odontogenic cyst, which are those 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 they 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 study from 2007, pineal gland cysts are fairly common.

Sebaceous cysts

People use the term “sebaceous cyst” to describe a type of cyst that occurs on the skin of the face, back, scalp, or scrotum.

Cysts that occur in these locations may be epidermoid or pilar cysts, though health professionals can only tell the difference after removing and analyzing the cyst.

Tarlov cysts

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

Vocal fold cysts

There are two types of vocal fold cyst: 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, called diplophonia
  • breathy speech, or dysphonia
  • hoarseness

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, they might 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.

Sometimes, a health 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.

Many 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.

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 needed.