Family doctor

What is a cyst?

Cysts are small cavities that have a lining membrane and contain fluid or semisolid material or air. They may occur as a result of a developmental error in the embryo before birth, or they may be caused by an infection, or, in some cases, they arise spontaneously and no cause is found.

Cysts can occur in almost any organ in the body. Sometimes they are an incidental finding when an ultrasound or CT scan is done for another reason and may never cause any problems. Such cysts are commonly seen in organs such as the liver, pancreas or kidney. A single cyst is likely to be an innocent finding, but multiple cysts, especially in the kidneys, can be indicative of polycystic kidney disease and may lead to renal problems.

 A few of the more common or important cysts are described here.

 1) Ovarian Cyst

An ovarian cyst is a fluid-filled sac in the ovary. It is most often normal, occurring as a result of ovulation; these are called 'functional cysts' and will normally shrink over time. They may occasionally cause pain if they rupture, or continue to grow, or if they bleed. They are usually demonstrated by ultrasound examination.

The management of an ovarian cyst depends on its size,symptoms whether there are solid areas, the age of the person and blood test results(CA125). In younger (pre menopausal women) with smaller benign cysts a follow up scan in 3-6 months to check that they have gone is a common strategy.

In post menopausal women,earlier investigation with aspiration and possibly biopsy is a safer strategy to ensure early ovarian cancer is diagnosed.

 2) Ganglion

A ganglion is a fluid-filled cyst that is connected to a joint or the 'tunnel' that surrounds finger tendons. They tend to occur on the back of the wrist or hand. The majority of these do not cause any pain or functional problem and can be left alone. They can sometimes even disappear spontaneously.

Occasionally they cause problems by pressing on a nerve and, in these cases, it is necessary to surgically remove the ganglion. Sometimes they are removed for cosmetic reasons,particularly if they are causing an unacceptable lump in an exposed area,

Ganglion surgery can often be done under local anaesthetic, but larger cysts, especially those on the wrist, may need a general anaesthetic.

 3) Baker's cyst

A "baker's cyst" appears as a swelling behind the knee, and is often associated with osteoarthritis of the knee joint. It is caused by a defect in the fibrous capsule that surrounds the joint and is filled with joint (synovial) fluid. If it causes persistent symptoms, a Baker's cyst can be surgically removed.

 4) Sebaceous cysts

These cysts occur in the skin in adults, typically on the trunk, neck, face or scalp. They are dome-shaped, appear whitish or skin-coloured and are filled with keratin, a semisolid compound that is the main component of hair, nails and skin.

They are usually painless, but may become red and painful if injured or infected. They are usually easily removed under local anaesthetic.

 5) Branchial and thyroglossal cysts

These cysts, which are uncommon, present as lumps in the neck. They are both a result of an error in embryonic development (before birth), but may appear only in adulthood.

Branchial cysts are filled with fluid containing cholesterol crystals. They appear on the front of the neck, on either side of the midline.

Thyroglossal cysts appear as a swelling in the midline of the neck, in front. They move on protruding the tongue.

Both of these types of cysts are treated by surgical removal.

 6) Breast cysts

Lumps in the breast may be caused by 'fibrocystic change'. These small cysts (1 to 5cm in diameter) may occur on their own and be difficult to distinguish from a malignant breast lump, but, more often, they are multifocal and often affect both sides. They may be painful and tender at certain times in the menstrual cycle.

You should always see a doctor if you detect any sort of breast lump.