Its rupture can create sharp, severe pain on the side of the ovary on which the cyst appears.

This sharp pain (sometimes called mittelschmerz) occurs in the middle of the menstrual cycle, during ovulation.

[citation needed] This type can form when ovulation doesn't occur, and a follicle doesn't rupture or release its egg but instead grows until it becomes a cyst, or when a mature follicle involutes (collapses on itself).

It is thin-walled, lined by one or more layers of granulosa cell, and filled with clear fluid.

[citation needed] Ultrasound is the primary tool used to document the follicular cyst.