Cysts: Causes, types, and treatments

Cysts are closed capsule or sac-like structures, typically filled with liquid, semisolid, or gaseous material, very much like a blister. In this article, we will describe the various types.

Cysts occur within tissue and can affect any part of the body. They vary in size from microscopic to the size of some team-sport balls. Very large cysts can displace internal organs.

In anatomy, a cyst can also refer to any normal bag or sac in the body, such as the bladder. In this article, cyst refers to an abnormal sac or pocket in the body that contains liquid, gaseous, or semisolid substances.

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 it is not a cyst; it is an abscess.

Fast facts on cysts

Here are some key points about cysts. More detail and supporting information is in the main article.

Cysts are usually noncancerous and have a sac-like structure that can contain fluid, pus, or gas.

Cysts are common and can occur anywhere on the body.

Cysts are often caused by infection, clogging of sebaceous glands, or around earrings.

It is unusual for cysts to cause pain unless they rupture, become infected, or inflamed.

Breast cysts are often painful and may be noticeable during a breast examination.

What causes cysts?

Cyst on wrist
Cysts can affect any part of the body.

Common causes of cysts include:


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

Benign and malignant cysts

Most cysts are benign and are caused by blockages in the body’s natural drainage systems. However, some cysts may be tumors that form inside tumors — these can potentially be malignant. Examples include keratocysts and dermoid cysts.

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Symptoms of cysts

Signs and symptoms vary enormously depending on what type of cyst it is. In many cases, a person becomes aware of an abnormal lump, particularly in cases with cysts of the skin or when a cyst is just below the skin.
A person may notice a cyst in their breasts when they examine them by touching them. Breast cysts are often painful.

Some cysts in the brain can cause headaches, as well as other symptoms.

Many internal cysts, such as those in the kidneys or the liver, may not have any symptoms and go unnoticed until an imaging scan (MRI scan, CAT scan, or ultrasound) detects them.

Types of cysts

Some of the most common types of cysts are listed below:

Acne cysts

Cystic, or nodulocystic, acne is a severe type of acne in which the pores in the skin become blocked, leading to infection and inflammation. You can read all about acne cysts in our other article: What is cystic acne?

Arachnoid cysts

The arachnoid membrane covers the brain. During fetal development the arachnoid membrane doubles up or splits to form an abnormal pocket of cerebrospinal fluid. In some cases, doctors need to drain the cyst. Arachnoid cysts may affect newborn babies.

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. Pain gets worse when extending the knee or during physical activity. Baker’s cysts are usually caused by a problem with the knee joint, such as arthritis or a cartilage tear.

Bartholin’s cysts

These may occur if the ducts of the Bartholin glands (situated inside the vagina) become blocked. Women may undergo surgery and/or be prescribed antibiotics.

Breast cysts

Breast cysts are often painful and usually need to be drained. Some studies have indicated that breast cysts may point to a raised breast cancer risk.

Chalazion cysts

Very small eyelid glands (meibomian glands) make a lubricant that comes out of tiny openings in the edges of the eyelids. Cysts can form if the ducts are blocked.

Colloid cysts

These are cysts that contain gelatinous material in the brain. In most cases, the recommended treatment is surgical removal of the cyst.

Dentigerous cysts

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