The Causes of Ovarian Cysts Follicular Cysts: These form when a follicle in the ovary fails to release an egg and instead develops into a cyst. Corpus Luteum Cysts: These occur when the follicle releases an egg but doesn't shrink as it should after ovulation. Dermoid Cysts: Uncommon cysts that can contain various tissues, including hair, skin, and teeth. Cystadenomas: These cysts develop on the surface of the ovaries and can be filled with a watery or mucous-like substance.