Pictures of vaginal cyst. Transillumination was negative. While most cysts won't cause any discomfort, you may notice signs that the cyst has become infected. Vaginal inclusion cysts are the most common type of vaginal cysts. It is necessary to wait until they are ready to be drained, which is when they are firm to the touch. Vaginal cysts are closed pockets of air, fluid, or pus located on or under the vaginal lining. Sometimes the openings of these glands become obstructed, causing fluid to back up into the gland. The growth of vaginal cysts is difficult to prevent. Vulvar procedures: Page last reviewed: Transillumination was negative.