Cyst, Clear
Synonyms/Description
Simple cyst
Clear ovarian cyst
Etiology
A simple ovarian cyst is a clear, thin-walled, unilocular cyst.
Premenopausal
Simple cysts up to 3 cm in maximal diameter are considered normal physiologic follicles in cycling women, and thus should not be reported as a cyst, particularly when the patient is midcycle. If a clear simple cyst does not resolve, it may be extraovarian, specifically paraovarian or paratubal. A persistent thin-walled and unilocular cyst may also represent a serous cystadenoma.
Postmenopausal
Small simple cysts up to 1 cm may be seen in up to 21% of postmenopausal women, and these are not considered clinically significant, even though the patient is no longer cycling. These less than 1 cm cysts typically should not be reported on an ultrasound examination and do not require follow-up.
In a study by Greenlee and colleagues, 2217 (14.1%) out of 15,735 women screened sonographically had one or more simple cysts on ultrasound examination. Among women without a cyst on the first screen, 8.3% had a new simple cyst 1 year later. There was no statistical difference in rate of subsequent ovarian cancer when those with simple cysts were compared with those without a cyst.
Ultrasound Findings
A simple and clear ovarian cyst is a thin, smooth-walled structure containing fluid with no internal echoes or solid areas. The cyst is usually round but can be oval, especially as it regresses and changes shape.
Any cyst that has a thick wall or any solid component is in a different category and discussed in other sections (refer to the differential diagnosis list for a complex cyst).
It is very important to scrutinize the sonographic appearance of cysts for any solid components or areas of wall thickening. A study by Valentin reports that 11 (0.96%) out of 1148 masses classified as unilocular cysts on ultrasound were malignant. However, postoperatively, 7 of the 11 malignancies thought to be unilocular cysts on ultrasound had gross papillary projections on the surgical specimen. Therefore accurate classification of a cyst as clear and unilocular is crucial on ultrasound examinations. Color Doppler may be useful to interrogate the walls of a cyst to better demonstrate any wall irregularity.
Differential Diagnosis
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