The classification of ovarian cysts is important because it helps guide therapy and treatment options. The first important question is weather the patient has gone through menopause. Cysts in a women that is postmenopausal are treated differently than cysts in the menstruating women. This discussion is for the woman who has not gone through menopause. Cysts are classified by their appearance, simple vs, complex. as well as the size. Some types of cysts can be diagnosed precisely with ultrasound, many can not.
A simple cysts is a cyst that is just a fluid filled sack. It is made up of only the cyst fluid and a smooth cyst wall. Complex cysts have some feature besides the fluid and cyst wall. Complex cysts may have growths inside the cyst or on the cyst wall called papillations or excrescences. Complex cysts may also have internal walls giving the appearance of several cysts stuck together. Simple are cysts are almost always benign, complex cysts are usually benign but could be cancerous.
The size of a cyst is also very important. It is a normal part of the ovarian function to have simple cysts less than 2 cm in size. When these are seen on ultrasound it is a normal finding. Cysts that are simple and between 2-5 cm almost always go away without treatment and do not cause any trouble. A cyst greater than 5 cm is large enough that it has the potential to rotate the ovary and cause the ovary to twist on itself, this is called an ovarian torsion. Ovarian torsions are very painful an require emergency surgery. They can be diagnosed on ultrasound by the lack of blood flow to the ovary. Simple cysts between 5-10 cm are usually followed with ultrasounds fairly closely but in some cases may need to be removed surgically. A simple cyst larger than 10 cm needs to be removed surgically as these are always abnormal and do not go away without surgery.
Complex ovarian cysts typically require surgery especially if they are persistent. The exception is a hemorrhagic cyst, these tend to go away on their own. A hemorrhagic cyst is caused when a small blood vessel ruptures during ovulation. This can bleed into the cyst causing a blood filled ovarian cyst. The blood eventually gets reabsorbed and the cyst goes away. Other complex ovarian cysts require surgery to rule out ovarian cancer. There are tumor markers that may be checked prior to surgery, specifically CEA and CA-125. If these are elevated the suspicion for cancer increases and the type of surgery required may be different.
An ovarian cyst with calcifications seen on ultrasound is almost always a dermoid cyst. Dermoid cysts are not cancerous but need to be removed surgically. They will not go away on their own and if they rupture they can cause significant problems. Dermoid cysts are interesting as they commonly have hair and teeth inside the cyst.