Evaluating Ovarian Masses on Ultrasound Part II

In terms of ovarian masses, among non neoplastic cysts, there is a modest list of them, but we’re really only interested in the top three.

The top three ovarian cysts are

1. The serous inclusion cyst, which is usually not large enough to be very clinically significant, but it is seen in both pre and post-menopausal women;
2. The follicular cyst, which is an accident of ovulation;
3. The corpus luteum cyst, which is an accident of ovulation.

So, if I think that it may be a non neoplastic cyst, then by all means I want to ask for a follow-up sonogram, because if the lesion disappears, then the patient can go back to her gynecologist with a sonogram report that says normal ovary.

So, size is important in non neoplastic cyst diagnosis. You’re looking for a lesion that is smaller than 6 cm in diameter. In any circumstance, non neoplastic cyst is going to be the more likely diagnosis, but in lesions that are under 6 cm in diameter, they are overwhelmingly the most common diagnosis.

Certain findings are typical of a non neoplastic cyst when you encounter an ovarian mass. Non neoplastic cysts tend to be unilocular cysts. We also know that neoplasms can be unilocular cysts, and here among 212 neoplasms that were unilocular cysts, you can appreciate that only 3 were malignant, and of those, two were greater than 10 cm in diameter.

So, if you have a unilocular cyst, the most likely diagnosis is that it is non neoplastic. If on a follow-up sonogram of one that is say smaller than 6 cm, it is still present, then you are reasonably confident that it is a benign lesion, a benign ovarian neoplasm.

One of the problems with unilocular cysts is that there are many varieties of unilocular cysts. The very common one are follicular cysts, corpus luteum cysts and the endometrioma.

Less likely are the paraovarian cysts, the serous inclusion cyst and the serous cystadenoma, our first neoplasm.

Uncommonly you will see cystic teratoma, mucinous cystadenoma and cystadenofibroma.

These are not uncommon neoplasm, they’re just uncommonly seen as unilocular cysts. Very rarely you will see a cystadenoma of low malignant potential or a serous cyst adenocarcinoma.

Here we have a unilocular borderline carcinoma seen in a 55 year old woman who obviously has a pretty sizeable lesion. This lesion obviously is going to be surgically excised. The surprise will be when a pathologist tells you it’s a borderline cancer.

In Part III we will discuss ways of ruling ovarian masses as benign with relative ease depending upon the type of ovarian mass.

Author: Roy A. Filly, MD
Excerpted from:
Diagnostic Imaging Review: For Residents, Fellows and Radiologists
Female Pelvis Section