A Patient’s Guide to Cysts
General information about different types of cysts

What is a cyst?
Cysts are small cavities with a lining membrane. They contain fluid or semisolid material or air. Cysts can occur almost anywhere in the body and may never cause any problems. While a single cyst is not likely to cause problems, multiple cysts can be problematic. 
Listed below are some of the major or important cysts:
Sebaceous cysts
These are cysts that occur in the skin, typically around the face or scalp. The cysts are dome shaped and are filled with keratin, a compound that is the main component of skin, hair, and nails. The domes are also whitish or skin-colored. The cysts are usually painless. However, they may turn red and painful if infected.
Branchial and thyroglossal cysts
These rare cysts show up as lumps in the neck, results of an error in embryonic development. However, the cysts may appear only in adulthood. Branchial cysts are filled with fluid containing cholesterol crystals, while thyroglossal cysts appear as a swelling in the middle of the neck. Both cysts can be removed surgically.
Breast cysts
Cysts in the breast may be caused by fibrocystic change. Unfortunately, these cysts may be difficult to distinguish from a malignant breast lump. They may be more painful and tender during the menstrual cycle. A lump of any kind in the breast must be looked at immediately by a doctor upon detection.
Ovarian Cyst
An ovarian cyst appears as a fluid-filled sac in the ovary. These cysts occur as a result of ovulation and will usually shrink over time, although they do cause occasional pain if they rupture or bleed. Ovarian cysts are managed according to size, symptoms, age of the person, and blood tests. Small benign cysts in young women usually go away. Post-menopausal women, on the other hand, should undergo further steps to make sure ovarian cancer is diagnosed. 
Ganglion
This is a fluid-filled cyst connected to a joint or the 'tunnel' that surrounds finger tendons. Ganglions tend to grow on the wrist or hand. The majority of these cysts does not cause any pain or functional problem and can be left alone. They can sometimes even disappear by themselves without treatment. However, ganglions can cause problems and complications as they press on a nerve; this might necessitate surgical removal of the ganglion. Sometimes they are also surgically removed for cosmetic reasons.
Baker's cyst
A "baker's cyst" is seen as a swelling behind the knee, and is often associated with osteoarthritis of the knee joint. This cyst is caused by a defect in the fibrous capsule that surrounds the joint and is filled with joint fluid. This cyst can be surgically removed if it causes further problems.