A cyst is a closed capsule or sac-like structure, usually filled with liquid, semisolid, or gaseous material. Cysts usually occur within a body's tissue; they vary in size from microscopic to large structures that can displace internal organs. Although "cysts" can also refer to any normal bag or sac formation in the body, in this article, we will use the definition stated above and consider it to be an abnormal formation. Consequently, the cyst is not a normal part of the body. It has a distinct membrane or cyst wall. If the sac is filled with pus, it is usually considered an abscess, not a cyst.
There are many causes of cyst formation. The following are some of the major causes of cyst formation:
· Errors in embryonic development
· Cellular defects
· Chronic inflammatory conditions
· Blockages of ducts in the body
There are hundreds of different types of cysts. Cysts can occur almost anywhere in the body. The majority of cysts are benign, but a few may contain malignant cells. The following cyst types may be found in the body:
· Epidermoid (sebaceous) cyst: usually benign swelling in the skin arising in the sebaceous gland, typically filled with yellowish sebum
· Breast cyst: a fluid-filled sac within the breast
· Ganglion or synovial cyst: a non-neoplastic soft-tissue collection that may occur in any joint
· Dermoid cyst: an abnormal growth containing epidermis, hair follicles, and sebaceous glands, derived from residual embryonic cells
· Ovarian cyst: an accumulation of fluid within an ovary that is surrounded by a very thin wall
· Baker cyst: a benign swelling of the membranous synovial bursa behind in the knee; also known as a popliteal cyst
· Bartholin cyst: formed when a Bartholin gland (at the opening of the vagina) is blocked
· Arachnoid cyst: a collection of cerebrospinal fluid covered by arachnoid cells and collagen that develops between the surface of the brain in the cranial base or on the arachnoid membrane
· Epididymal cyst: extratesticular spherical cysts in the head of the epididymis
· Labial cyst: any fluid-filled cyst in the labia
· Pilonidal cyst: a cyst that contains hair and skin debris near or on the cleft of the buttocks; also known as jeep driver's disease
· Nabothian cyst: a mucous-filled cyst on the surface of the cervix
· Pineal cyst: a fluid-filled body in the pineal gland (of the brain)
· Thyroglossal cyst: a fibrous cyst that forms from a persistent thyroglossal duct
· Synovial cyst: also known as a ganglion cyst, is a soft tissue lump that may occur in any joint
· Branchial cleft cyst: a cyst composed of epithelial cells that arise on the lateral part of the neck due to congenital failure of obliteration of the second branchial cleft
· Choroid plexus cyst: small cysts composed of cerebrospinal fluid trapped by spongy brain cells
· Hydatid cyst: spp. tapeworm (larval stage) surrounded by epithelial cells in an organ
· Corpus luteum cyst: a type of ovarian cyst that may persist after an egg has been released from a follicle
· Colloid cyst: in the brain, a cyst containing gelatinous material
· Mucous cyst: a thin sac containing clear fluid that may be found on the lips, mouth, and occasionally in other areas of the body
· Pancreatic cyst: sac-like pockets of fluid within the pancreas; technically, they aren't cysts because they are lined with scar or inflammatory tissue
· Testicular cysts: fluid-filled cysts in the testicles
· Thyroid cysts: Also called a thyroid nodules, they may be fluid filled or contain some solid components; most are benign but a few may contain malignant components.
· Liver cysts: thin-walled cysts that contain fluid; the majority are benign
· Kidney cyst: walled-off fluid-filled areas within the kidney; some are congenital (polycystic disease)
· Sinus cysts: abnormal tissue growth, usually in the maxillary sinuses, filled with liquid, air, or semisolid material
· Acne cyst: aggregations of inflamed and clogged skin oil ducts; many are not cysts but are abscesses
Readers should note that many cysts types are not listed; the purpose of this article is to give the reader an introduction to the hundreds of types of cysts and is not meant to be all-inclusive.
The risk factors for a cyst depend on the underlying cause. Genetic conditions, defects in developing organs, infections, tumors, and any obstructions to the flow of fluid or oils or other substances are risk factors for cyst development.
The majority of small cysts have no symptoms or signs. However, sometimes the cysts can be felt as a lump or bump in the skin or even in the tissues beneath the skin. Sometimes these cysts are painful. Cysts not associated with the skin but with internal organs may not produce any symptoms if they are small. If the cysts become large and displace or compress other organs or block normal fluid flows in tissues like the liver, pancreas, or other organs, then symptoms related to those organs may develop.
The doctor easily palpates some cysts, especially if the cysts are located in the skin or in organs that are readily palpable, like the thyroid gland. Imaging studies such as ultrasound, X-ray, CAT scans, and MRIs are very useful in finding cysts. In addition, needle biopsies are sometimes used to determine if malignant tissue is associated with a cyst-like structure and may be used to reduce the size of the cyst.
The treatment for a cyst depends on the underlying cause of the cyst and whether or not the cyst is causing the patient problems. As stated previously, many cysts are benign and require no treatment. However, large cysts can result in symptoms due to compression of normal tissue and obstruction of ducts. Some of these cysts can be treated by simply aspirating the cyst contents through a needle or catheter, thereby collapsing the cyst. Other cysts require surgical removal, especially if there's any suspicion of malignancy. Self-treatment by squeezing or popping a cyst is not advised because it could exacerbate the underlying cause in some individuals.
The prognosis of a cyst depends upon its underlying cause and sometimes on its size. The majority of cysts are small and benign; they require no treatment and have a good prognosis. However, cysts that are associated with infective agents or contain malignant cells or are so large they interfere with normal body functions have a more guarded prognosis. Some benign but large cysts may have a fair to good prognosis but may require surgery or aspiration to reduce or eliminate symptoms.
Most cysts are not preventable; however, if an underlying cause of a cyst is prevented, then the resultant cyst may also be prevented (for example, cysts due to infectious agents).