Clinical Review

A guide to management: Adnexal masses in pregnancy

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Forego surgery in most cases until delivery—or until the risky first trimester has passed



CASE 1 An enlarging cystic tumor

A 20-year-old gravida 3 para 1011 visits the emergency department with persistent right flank pain. Although ultrasonography (US) shows a 21-week gestation, the patient has had no prenatal care. Imaging also reveals a right-sided ovarian tumor, 14×11×8 cm, that is mainly cystic with some internal echogenicity.

At 30 weeks’ gestation, a gynecologic oncologist is consulted. Repeat US reveals the mass to be about 20 cm in diameter and cystic, without internal papillation. The patient’s CA-125 level is 12 U/mL. Based on this information, the physicians decide the likely finding is a benign ovarian cystadenoma.

How should they proceed?

The discovery of an adnexal mass during pregnancy isn’t as rare as you might think—depending on when and how closely you look, it occurs in about 1 in 100 gestations. In most cases, we have found, the mass is clearly benign (TABLE 1), warranting only observation.


Adnexal masses removed during pregnancy: Histologic profile

Cystadenoma549 (33)
Dermoid451 (27)
Paraovarian/paratubal204 (12)
Functional237 (14)
Endometrioma55 (3)
Benign stromal28 (2)
Leiomyoma23 (1.5)
Luteoma8 (0.5)
Miscellaneous55 (3)
Malignant68 (4)
Data supplied by the authors from surgical experience

In the case described above, the physicians followed the patient and removed the mass at term because it was cystic with no other indications of malignancy. At 37 weeks’ gestation, a cesarean section was performed through a midline laparotomy incision, followed by removal of the ovarian tumor, which was benign. The pathologist measured the tumor at 16×12×4 cm and determined that it was a corpus luteum cyst.

Presence of mass raises questions

Despite the rarity of malignancy, the discovery of an ovarian mass during pregnancy prompts several important questions:

How should the mass be assessed? How can the likelihood of malignancy be determined as quickly and efficiently as possible, without jeopardy to the pregnancy?

When is surgical intervention warranted? And when can it be postponed? Specifically, is elective operative intervention for a tumor that is probably benign appropriate during pregnancy?

When is the best time to operate? And what is the optimal surgical route?

In this article, we address these questions with a focus on intervention. As we’ll explain, only a small percentage of gravidas who have an adnexal mass require surgery during pregnancy. When surgery is necessary, it is usually indicated for an emergent problem or suspicion of malignancy. Even when ovarian cancer is confirmed, we have found that it is usually in its early stages and therefore has a favorable prognosis (TABLE 2).


Malignant adnexal masses removed during pregnancy

Epithelial101 (28)
Borderline epithelial147 (40)
Germ-cell dysgerminoma47 (13)
Other34 (9)
Stromal24 (7)
Undifferentiated5 (1.4)
Sarcoma2 (0.5)
Metastatic4 (1.1)
Data supplied by the authors from surgical experience

How should a mass be assessed?

Ultrasonography and other imaging often reveal the presence of a mass and help determine whether it is benign or malignant. In fact, most adnexal masses discovered during pregnancy are incidental findings at the time of routine prenatal US. (see the most commonly found tumors.) Operative intervention is required in 3 situations:

  • malignancy is suspected
  • an acute complication develops
  • the sheer size of the tumor is likely to cause difficulty.

Common adnexal tumors found during pregnancy

Corpus luteum

A persistent corpus luteum is a normal component of pregnancy. Although it usually appears as a small cystic structure on ultrasonographic imaging, the corpus luteum of pregnancy can reach 10 cm in size. Other types of “functional” ovarian cysts may also be found during pregnancy. Most functional cysts resolve by the early second trimester.4,6 In rare cases, a cyst may develop complications such as torsion or rupture, causing acute pain or hemorrhage. Otherwise, a cystic tumor identified in the first trimester should be characterized and followed using ultrasonography (US).

Benign neoplasm

An adnexal mass that persists beyond the first trimester is more likely to be a neoplasm.3-5,10,11,22 Such a mass is generally considered clinically significant if it exceeds 5 cm in diameter and has a complex sonographic appearance. Usually such a neoplasm will be a benign cystadenoma or cystic teratoma.5,10-13,19,23,24

Benign cystic teratoma

This tumor can be identified with a fairly high degree of specificity using a variety of imaging techniques, with management based on the presumptive diagnosis. This tumor is unlikely to grow substantially during pregnancy. When it is smaller than 6 cm, such a tumor can simply be observed.14 A larger tumor can occasionally rupture or lead to torsion or obstruction of labor, but such occurrences are rare.

Benign cystadenoma

In an asymptomatic patient with imaging that suggests a benign cystadenoma (see sonogram), benign cystic teratoma, or other benign tumor, observation is reasonable in most cases.4,6,7,9-11,14,19 Operative intervention is required when there is less certainty regarding the benign nature of the tumor, an acute complication develops, or the tumor is expected to pose problems because of its large size alone.

Uterine leiomyoma

It is rare for an ovarian tumor detected during pregnancy to have a solid appearance on US. When it does, it may be a uterine leiomyoma mimicking an adnexal tumor (see intraoperative photograph). It should be reevaluated with more detailed US or magnetic resonance imaging.25


About 10% of adnexal masses that persist during pregnancy are malignant, according to recent series.4,5,7-10,12,13,24,26

Most of the ovarian cancers diagnosed during pregnancy are epithelial, and a substantial portion of these are low-malignant-potential (LMP) tumors.5,10,11,13,19,23,24,26,27 This ratio is in keeping with the age of these women, which also explains the stage distribution (most are stage 1) and the large percentage of germ-cell tumors detected. The majority of ovarian cancers discovered in pregnant women have a favorable prognosis.

Benign-appearing cystadenoma

A morphologically benign-appearing, large, cystic adnexal mass can be seen in association with an 11-week gestation.

Leiomyoma mimics an ovarian tumor

This 17-week gestation was marked by a large pedunculated leiomyoma that at fist appeared to be a right adnexal tumor.


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