Womens Health

How to tell if an Ovarian Mass is Malignant

Frederick R. Jelovsek MD

Just as a breast lump is frightening because it may mean cancer, so is a pelvic mass that the doctor thinks may possibly be ovarian cancer. Most women, if given a choice, would rather have a gynecologic oncologist who has had specialized training do the surgery. This is especially true if they knew that the mass was going to turn out to be malignant and spread beyond the ovary. Most local hospitals do not have a gynecologic cancer specialist on staff, so the dilemma becomes "what criteria should be used to strongly recommend that a woman have her surgery at a regional center?"

A recent study in Norway looked how to predict whether a woman with possible ovarian malignancy should be referred to the regional cancer center. Tingulstad S et al: The risk-of-malignancy index to evaluate potential ovarian cancers in local hospitals. Obstet gynecol 1999;93:448-52.They looked at 365 women from seven local hospitals that were evaluated with a risk scoring system to see if they should be transferred to the central cancer hospital. This study answers several questions about the ultrasound findings, age, menopausal status and CA 125 serum test measurement (an ovarian cancer antigen) and how they can be used to predict the chance of malignancy.

Can the doctor tell if an ovarian tumor is malignant by vaginal ultrasound?

Malignancy of the ovary cannot be diagnosed with any certainty by ultrasound. The best that can be done is to identify characteristics that make it more likely to be malignant or benign. There are many benign pelvic conditions that can appear on ultrasound as worrisome for malignancy. These include: benign epithelial and functional ovarian cysts, hemorrhagic ovarian cysts, endometriosis, dermoid cysts (benign teratomas), ovarian fibroids, uterine fibroids, fimbrial cysts, hydrosalpinges (swollen, fluid-filled faloppian tubes), pelvic abscesses, pelvic adhesions, bowel adhesions and adenomyosis.

How common are ovarian malignancies in younger women?

If you look at the distribution of ages in this study (confined to women over 30), you will see that benign tumors and causes of ovarian masses can occur in all age ranges. Malignancy of the ovary definitely is higher in older women and lower in frequency in the younger ages.

Risk of Malignancy Age Distribution

Age
(years)
Benign
(n=290)
Malignant
(n=75)
30-44 106 (37%) 11(15%)
45-54 104 (36%) 17(23%)
>=55 80 (28%) 47(63%)

After menopause, are not most ovarian masses malignant?

Just as there is an increased chance of an ovarian tumor being malignant at older ages, so is the chance after menopause. Benign pelvic/ovarian masses occur with almost equal frequency before and after menopause.

Risk of Malignancy Distribution by Menopause

Menopausal
status
Benign
(n=290)
Malignant
(n=75)
Premenopause 175 (60%) 18 (24%)
Postmenopause 115 (40%) 57 (76%)

Does the CA-125 test accurately predict ovarian cancer?

CA-125 is an ovarian cancer antigen test but it is also positive in many cases of benign pelvic and abdominal disease, especially premenopausal. Fibroids, diverticulitis, liver disease, benign ovarian tumors, endometriosis and other nonmalignant sources can cause an elevation in CA-125. Normal values in most labs are 35 u/ml or less and only when the values are over 100 u/ml is there a great concern for malignancy. Benign causes can be associated with levels higher than 100 u/ml while malignancies, especially early Stage I ovarian cancer can be associated with normal or equivocal levels (35-100 u/ml).

Risk of Malignancy Distribution by CA-125 Level

CA-125 (u/ml) Benign
(n=290)
Malignant
(n=75)
Mean
(average of values)
42 611
Median
(middle value)
17 95
Range
(lowest to highest)
1-2700 8-11,260

 

What changes on ultrasound are most worrisome for malignancy?

There have been different ultrasound scoring systems to try to predict malignancy. Anytime the ultrasonographer sees the following characteristics, there may be an increased chance of malignancy beyond just a simple cyst:

  • multiloculated cysts (septations within a cystic area)
  • solid areas
  • bilateral lesions
  • ascites (fluid in the pelvic/abdominal cavity)
  • evidence suspicious for intraabdominal metastases


Giving a score of one for any of the above findings, the risk of malignancy cases were divided into :

Risk of Malignancy by Ultrasound Findings

Ultrasound score Benign
(n=290)
Malignant
(n=75)
0 79 (27%) 3 (4%)
1 112 (39%) 13 (17%)
2-5 99 (34%) 59 (79%)



Note that many (34%) benign masses have more than one characteristic of malignancy.

When does the chance of ovarian cancer increase enough that it is best to have the initial surgical exploration done by a gynecologic cancer surgeon specialist?

The authors in the Risk of Malignancy study used a scoring system by Jacobs (1990) based on the menopausal status (premenopausal = 1, postmenopausal = 3), ultrasound characteristics (zero or one characteristic ultrasound finding = 1, two or more features = 3) and the CA-125 level (actual value). They then multiply these three values together (RMI= M X U X Ca-125). For example, a postmenopausal woman (3) who had two ultrasound characteristics of malignancy (3) and had a CA-125 level of 50 u/ml, would have a risk of malignancy index (RMI) of 3x3x50 =300. In calculating RMIs for all the patients in their study, Tingulstad et al found:

Risk of Malignancy by Ultrasound Findings

Risk-of malignancy
cutoff
Benign
(negative predictive value)
Malignant
(positive predictive value)
50 94% 35%
100 93% 49%
150 92% 59%
200 92% 69%
250 92% 73%
300 92% 76%


In other words, if a cutoff of RMI=300 is used to predict whether there may be a malignancy present, if the RMI is 300 or over, 3 out of 4 times an ovarian malignancy will be present. If it is less than 300 and a woman stays at the local hospital, 8% of the time (1 out of 12 times) an ovarian malignancy will be found. In this study, none of the Stage 2-4 ovarian cancers and none of the Stage 1C ovarian cancers would be performed in the local hospital. These are excellent findings because almost all gynecologic surgeons can do the surgery needed to fully treat Stage 1 A and B (confined to the ovary (s) and not spread) ovarian cancer.



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