How much does a ovarian cystadenoma scare me?

Very little: Cystadenomas are benign and do not develop into cancer. If they are larger than 5 cm, they can twist and damage the ovary, or they can rupture causing pain. Furthermore, until they are removed, the fact that they are benign rather than borderline malignant or malignant, is hard to tell with certainty. For the above reasons, removal is recommended. But once removed, no worries!