Cancer complicates 1:1,000 pregnancies in the United States. The most common malignancies seen in pregnancy include malignant melanoma (2.6:1,000), Hodgkin lymphoma (1:1,000-6,000), breast cancer (1:3,000-10,000), cervical cancer (1.2:10,000), ovarian cancer (1:10,000-100,000), colorectal cancer (1:13,000), and leukemias (1:75,000-100,000).

The lifetime risk of developing ovarian cancer is 1.4% (14 per 1,000), the highest risk occurring after menopause. Women of reproductive age have a low risk approximating 0.2% to 0.4%. Benign ovarian tumors are the most common complicating pregnancy. The exact incidence, however, depends on whether one considers simple cysts noted on ultrasound examination (1 in 50 live births), during pelvic examination (1in 80 live births), or those that ultimately require laparotomy (1 in 1,000 to 1 in 1,500 live births). Hill and colleagues reported findings for ovarian cysts found at the time of secondand third-trimester ultrasound. Ovarian cysts were diagnosed in 4.1% of second- or third-trimester ultrasounds. Most of these cysts were less than 3 cm and resolved spontaneously. Eighteen of the 7,996 patients had an exploratory laparotomy, which was equivalent to one surgery in 444 deliveries. All of these lesions were benign on pathologic examination. Ueda and Ueki reported 106 patients who required ovarian surgery during pregnancy. Of these patients, 31 (29.2%) had physiologic ovarian cysts, 70 (66%) were benign tumors, and 5 (4.7%) were malignant. More recent observations by Schlemer et al. have noted that adnexal masses greater than 5 cm were observed in 63 patients (0.05%), with 4 patients (6.8% of masses and 0.0032% of deliveries) diagnosed as malignant. Finally, these tumors may also be an incidental finding at the time of cesarean. Koonings and colleagues noted the incidence of ovarian tumors complicating cesarean section to be about 1 in 200 cesarean births. Dede et al. also observed a 0.8% incidence of masses greater than 5 cm at the time of cesarean section.

Benign neoplasms complicating pregnancy include two tumorlike conditions with which every gynecologist should be familiar. Hyperreactio luteinalis (first described by Burger in 1938 as a grossly multicystic, usually bilateral ovarian enlargement, often 15 to 20 cm in size) is a term used to describe numerous luteinized follicular cysts of the ovary complicating pregnancy. Microscopically, one notes extensive luteinization of the theca and granulosa cell layers. Bradshaw and associates suggest that the hyperandrogenicity seen in this condition is related to increased ovarian sensitivity to hCG. Therefore, it is seen in conditions in which the hCG is elevated, such as hydatidiform mole, multiple gestations, choriocarcinoma, and erythroblastosis fetalis. Hyperreactio luteinalis also has been associated with normal pregnancy, and, in these patients, it has not been associated with fetal virilization. These tumors spontaneously regress after delivery but may take up to 6 months to resolve. Hyperreactio luteinalis also may occur in subsequent pregnancies.

Luteoma of pregnancy is a specific benign, usually unilateral, solid lutein cell tumor of the ovary found in late pregnancy, often noted at cesarean section (Fig. 35B.2A, B). First described by Sternberg in 1966, this tumor is grossly bosselated, soft, fleshy, yellow, or hemorrhagic. Microscopically, it exhibits an acidophilic granular cytoplasm with sparse lipid formation and a distinctive reticular pattern. It is likely the most common cause of maternal virilization during pregnancy. The etiology is unknown, but theories have included luteinized stromal cells present before pregnancy that respond to hCG or “hyperluteinized” theca cells, granulosa cells, or a combination of the two. Fifty percent of female infants born to virilized mothers with pregnancy luteoma exhibit signs of virilization.

The important clinical implication with both of these lesions is that if they are recognized or suspected, simple biopsy without further surgery is adequate therapy, because both invariably resolve spontaneously.

The most common benign neoplasm of the ovary in pregnancy is the benign cystic teratoma, which accounts for about one third of all benign ovarian tumors seen in pregnancy (Fig. 35B.3A, B). The second most common group of ovarian tumors complicating pregnancy is that of cystadenomas (Fig. 35B.4). These represent about 15% of tumors. Endometriomas, simple cysts, corpus luteal cysts, tubal cysts, myomas, and other miscellaneous lesions constitute the remaining types of tumors seen in pregnancy (Table 35B.1).

Malignant ovarian tumors constitute only about 1% to 2% of all adnexal masses that complicate pregnancy and require
surgical exploration. The single most common malignant ovarian tumor complicating pregnancy probably is dysgerminoma. Malignant tumors of epithelial origin as a group, however, are more common (Fig. 35B.5); tumors of low malignant potential occur most frequently (Fig. 35B.6). Sex-cord stromal tumors are the third most common primary malignant ovarian neoplasms, representing about 17% to 20% of such tumors. Krukenberg and other metastatic tumors represent about 12% to 13% of malignant ovarian neoplasms complicating pregnancy (Fig. 35B.7).

Whether malignant or benign, most ovarian tumors complicating pregnancy are unilateral. Karlen and associates reported 90% of dysgerminomas in pregnancy to be unilateral, and Young and colleagues reported 35 of 36 sex-cord stromal tumors to be unilateral when complicating pregnancy. Even malignant tumors of epithelial origin noted during pregnancy are unilateral in 90% of cases. The rarer germ cell tumors, such as endodermal sinus tumors, virtually always are unilateral as well. It is also interesting that most bilateral tumors occurring in pregnancy are not malignant; these include benign cystic teratoma, endometriosis, and hyperreactio luteinalis. The most common bilateral malignant ovarian tumors are the metastatic Krukenberg types. Somewhat less common are primary malignant tumors of epithelial origin.