Three major categories account for virtually all malignant ovarian tumors. Organization of these groups is based on the anatomic structures from which the tumors originate (Fig. 36-1). Epithelial ovarian cancers account for 90 to 95 percent of malignant ovarian tumors (Chap. 35). Germ cell and sex cord-stromal ovarian tumors account for the remaining 5 to 10 percent and have unique qualities that require a special management approach (Quirk, 2005).
Origins of the three main types of ovarian tumors. (Adapted with permisison from Chen VW, Ruiz B, Killeen JL, et al: Pathology and classification of ovarian tumors, Cancer 2003 May 15;97(10 Suppl):2631–42.)
MALIGNANT OVARIAN GERM CELL TUMORS
Germ cell tumors arise from the ovary’s germinal elements and make up one third of all ovarian neoplasms. The mature cystic teratoma, also called dermoid cyst, is by far the most common subtype. This accounts for 95 percent of all germ cell tumors, is clinically benign, and discussed in Chapter 9. In contrast, malignant germ cell tumors compose 2 to 3 percent of malignant ovarian cancers in Western countries and include dysgerminoma, yolk sac tumor, immature teratoma, and other less common types.
Three features distinguish malignant germ cell tumors from epithelial ovarian cancers. First, individuals typically present at a younger age, usually in their teens or early 20s. Second, most have stage I disease at diagnosis. Third, prognosis is excellent—even for those with advanced disease—due to exquisite tumor chemosensitivity. Fertility-sparing surgery is the primary treatment for women seeking future pregnancy, although most will require postoperative chemotherapy.
The age-adjusted incidence rate of malignant ovarian germ cell tumors in the United States is much lower (0.4 per 100,000 women) than that of epithelial ovarian carcinomas (15.5) (Quirk, 2005). Smith and associates (2006) analyzed 1262 cases of malignant ovarian germ cell from 1973 to 2002 and observed that incidence rates have declined 10 percent during the past 30 years. Unlike a significant proportion of epithelial ovarian carcinomas, malignant germ cell tumors are not generally considered heritable, although rare familial cases are reported (Galani, 2005; Stettner, 1999).
These tumors are the most common ovarian malignancies diagnosed during childhood and adolescence, although only 1 percent of all ovarian cancers develop in these age groups. At age 20, however, the incidence of epithelial ovarian carcinoma begins to rise and exceeds that of germ cell tumors (Young, 2003).
The signs and symptoms associated with these tumors vary, but in general, most originate from tumor growth and the hormones they produce. Subacute abdominal pain is the presenting symptom in 85 percent of patients and ...