A complex ovarian cyst is a cyst that has more than one kind of layer inside. There are three common kinds of complex ovarian cysts. Cystadenomas fill with watery mucus. They can grow to a foot (300 mm) or more in diameter. Although cystadenomas are not cancerous, they usually excruciatingly painful. They can twist the ovaries so that circulation is cut off (and the ovary can no longer release eggs), but thankfully these complex cysts are rare. Dermoid cysts are stem cells, the same kind of stem cells you may have heard about in the news. These ovarian cysts form from unfertilized eggs. They have the potential to transform themselves into other kinds of tissue, and they usually do. As horrifying as it sounds, they can even develop skin, hair, and teeth. When they grow large enough to twist the ovaries, they also can cause excruciating pain. Since they usually affect only one ovary, they do not necessarily cause infertility. The third kind of common complex ovarian cyst is the endometrioma. As its name suggests, an endometrioma is a bit of the endometrium, or lining of the uterus, that got broken off and lodged in an ovary. Since the lining of the uterus grows during the first 14 days of the menstrual cycle, the endometrioma also grows during the first 14 days of the menstrual cycle, stimulated by estrogen.
The bigger the complex cyst, the more painful it will be. Complex cysts cause an odd kind of menstrual pain that can radiate out to the buttocks and thighs. Since ectopic pregnancy also causes this kind of pain, and ectopic pregnancy is a life-threatening emergency, it is essential to seek immediate medical attention when women experience severe, sudden pain in the abdomen, especially if it radiates to the buttocks and thighs. Unlike PCOS, complex cysts usually affect only one ovary and do not interfere with a woman's hormonal balance. They are not likely to cause infertility. But since their presence can make pregnancy unsustainable, it is always important to have any abdominal pain or lumpiness checked out by a doctor.