Evaluating Ovarian Masses on Ultrasound Part IV

Continuing our discussion of ovarian masses you may encounter when performing ultrasound, which neoplasms have a high probability of being malignant?

This actually isn’t so difficult to evaluate either, with practice. Any multiseptate mass, particularly any one that has a septal nodule or septal nodules, are highly predictive of malignancy. Avery large multiseptate mass with a thickened and irregular wall, and obviously any solid mass is under suspicion of malignancy.

Not all solid masses are malignant, we do have the benign fibroma thecoma group and the Brenner cell tumors, but the important message is to carry away with you is that all solid neoplasms of the ovary belong in a pan.

Now I do not know how your examiner will feel about Doppler sonography of ovarian masses. Personally I am not particularly in favor of spectral Doppler sonography to evaluate ovarian masses.

It is very likely that your examiner will also not be very happy with this as a way of examining ovarian masses.

However, you should be aware of the principals involved if you’re asked and that is, the principal is that benign lesions tend to demonstrate high resistance to arterial flow, whereas malignant lesions demonstrate low resistance.

That’s because the neovessels that form in the malignant neoplasms have very poorly formed muscular walls. Therefore, they cannot squeeze down and mount resistance.

That statement is true but it is otherwise not a very helpful finding.

Any lesion is considered relatively high resistance if the resistive index is greater than .4, so if we look at a .74, we might say at first glance that looks benign, but actually morphologically, we would say this is a hemorrhagic cyst, so not only is it benign, but it would almost certainly go away on its own.

Is Doppler the answer to telling us whether or not the lesion is benign or malignant? In my opinion, the answer is no, it’s not the way to tell. Let’s take an example of  a 65 year old woman who has a huge mass with thick septi and this gigantic mural nodule. This is almost certainly a malignancy.

But when we start to examine her for resistive indexes, we see that that portion of the tumor has a very high resistive index, and it’s not until we find a little daughter cyst here that we find a low resistance signal.

The lesson being the following: That if you measure the resistance index in a whole bunch of benign lesions and a whole bunch of malignant lesions, you will find that the mean difference in resistive index between the benign and malignant group will show that the malignant group will have a lower resistive index and the difference between then will likely be statistically significant.

It doesn’t tell you whether the lesion is benign or malignant. The reason for that is that resistive indices vary all over the map in any given ovarian neoplasm.

Practice in looking at ultrasound helps enormously, because as we have discussed, with experience, you can confidently rule out cancer in many instances with one or two ultrasound images.

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