What Causes Cysts and When to Worry

A cyst is a pocket or pouch of tissue filled with air, pus, fluid, or other material. They can form in any tissue in the body, and where they form can affect what is inside of them. For example, cysts in the lungs are typically filled with air, while cysts in the kidneys or liver are generally fluid-filled.

Cysts are not a part of normal tissue. A cyst has its own wall, separating it and the material inside of it from the tissue it is growing in. Cysts can range in size from very small to several inches in diameter. Depending on the size, type, and location, some cysts can be left alone, but they may also need to be drained or removed.

Cysts located under the skin often feel like a smooth, firm lump. They can swell or become red and may be painful.

Internal cysts may not cause symptoms and are often found on scans. These are usually discovered during imaging for unrelated issues.

A number of things can cause cysts. Common causes include infections, genetics, hormonal shifts, inflammation, and blocked ducts or glands.

Multiple types of cysts can form on the skin. For example, epidermoid or sebaceous cysts are filled with keratin, a protein that forms the structure of the skin and typically appears on the face, neck, and trunk.

Pilar cysts, which are also filled with keratin, can form on the scalp. These cysts may progress slowly and remain for years. They may rupture or become infected, though serious complications are rare.

Ovarian cysts are common in menstruating individuals, and often occur during ovulation. There are two main types of ovarian cysts. In a typical menstruation cycle, the ovary releases an egg every month.

The egg grows in a sac inside the ovary called a follicle. The follicle breaks open when the egg matures, releasing it. A follicle cyst can form when the follicle does not release the egg and, instead, it keeps growing, forming a cyst.

These cysts typically have no symptoms and go away on their own within three months.

When the follicle does release the egg, the empty sac collapses into a mass of cells called the corpus luteum, which makes hormones in preparation for the next menstrual cycle.

If the sac does not shrink, it will reseal itself after releasing the egg, trapping fluid inside, and forming a corpus luteum cyst.

These cysts usually go away after a few weeks, but they can grow up to four inches wide and cause pain or bleeding or twist the ovary.

Breast cysts are a common diagnosis and often change with the menstrual cycle. They can vary in size, ranging from small microcysts to larger cysts.

Some people may develop a single cyst, while others may have multiple cysts. Typically, these cysts are asymptomatic and may be discovered via a mammogram or other scan.

In some cases, they may become palpable under the skin or cause pain or nipple discharge. Breast cysts are generally filled with fluid. If they grow large enough to cause pain, they may require draining.

If multiple or complex cysts are present, more testing, like a breast ultrasound or biopsy, may be necessary to rule out cancer.

Thyroid cysts can be small and asymptomatic, but if they grow, they can cause lumps in the neck as well as pain or difficulty swallowing.

These cysts are nearly always benign, but they can have solid parts that can become cancerous.

Thyroid cysts generally do not cause fluctuations in hormone levels, but they can in some cases, particularly if they are large, complex, or turn into a nodule.

Simple kidney cysts can occur with conditions that impair kidney function and often appear on the surface of the kidney.

In many cases, a single cyst can develop on one kidney, but multiple cysts can occur on one or both kidneys.

Simple kidney cysts generally do not have symptoms, but if they grow large enough, they can cause fever or pain in the back, side, or upper abdomen, press against other organs, and require monitoring or interventions.

Simple kidney cysts should not be confused with polycystic kidney disease, a genetic condition in which numerous cysts form and lead to kidney enlargement and dysfunction.

Brain cysts can contain pus, blood, or cerebrospinal fluid and be benign or malignant. Even brain cysts that are not cancerous can cause problems, depending on their size and location.

Small cysts that are not growing and are unlikely to cause problems may require monitoring. Cysts that press on brain tissue and cause nausea, vision issues, or headaches may require surgery.

Some brain cysts are present from birth, while others can appear after an injury or infection.

Spinal cysts are more common in people over 50and may result from spinal instability or degeneration.

They are common in the lower part of the spine, particularly in people who have arthritis or disk disease. Treatment can involve anti-inflammatory medication, rest, drainage, or steroid injections, though these are generally short-term solutions.

If spinal cysts become large or impair movement, surgery may be recommended for longer-lasting relief.

Cysts are closed sacs that usually contain fluid and are generally painless. They grow slowly but can cause pain and other complications if they grow too large.

Boils are painful pus-filled lumps that are caused by a bacterial infection. Treatment for cysts depends on the size and location. Small cysts may resolve on their own, while large or complex cysts may require drainage or surgery.

Boils, by contrast, are typically treated with antibiotics.

Talk to your doctor if you have a cyst that is painful, continues to grow, or does not resolve on its own. Cysts that change color or shape or cause other symptoms may need in-depth testing or monitoring.

Most cysts are benign, but some can turn cancerous or lead to other complications. A doctor can help rule out more serious conditions and recommend the right treatment.