The 3 major types of ovarian tumors are epithelial, sex cord, and germ cell. Epithelial cell tumors represent the majority of all ovarian neoplasms (82%). Conversely, germ cell tumors (GCTs) are rare, comprising approximately 20% of all ovarian tumors, both benign and malignant. Approximately 3-5% of ovarian GCTs are malignant. The most commonly occurring GCT is the dysgerminoma, which accounts for approximately 2% of all ovarian cancers.
Although rare, dysgerminomas are important irrespective of incidence because they most commonly affect women of reproductive age (ie, < 30 y). In fact, dysgerminomas make up two thirds of all malignant ovarian neoplasms in women younger than 20 years. Moreover, once diagnosed, dysgerminomas respond well to therapy, potentially sparing patients from infertility and early mortality.
Typically, germ cells are encapsulated at birth within the primordial follicle. If they somehow escape encapsulation, cell death usually occurs. If the germ cells survive, rapid growth ensues, owing to the lack of normal contact inhibition, hence germ cell tumor (GCT) formation. All dysgerminomas are considered malignant, but only one third of dysgerminomas behave aggressively. The exact etiology of dysgerminomas has not been determined, although recent molecular studies have implicated loss of function with potential tumor suppressor gene TRC8/RNF139 as a possible etiology. 
Additionally, 5% of all dysgerminomas occur in dysgenetic gonads and may be associated with gonadoblastomas. Genetic disorders of the ovary are associated with karyotypic abnormalities and are discussed in Dysgerminomas in patients with karyotypic abnormalities in Complications.
The incidence of dysgerminomas has remained unchanged over the last 30 years. The frequencies of the most common malignant ovarian neoplasms in women of reproductive age are as follows: epithelial tumors (42%); dysgerminoma and other germ cell tumors (GCTs) (30%); metastatic Krukenberg tumors (14%); and sex cord stromal tumors (ie, Sertoli-Leydig cell tumors) (13%).
No data are available.
The 5-year survival rate is 96% if the tumor is confined to the ovary and 63% if extension occurs beyond the ovaries. Pregnancy does not alter the prognosis of most ovarian malignancies, but complications such as torsion and rupture may increase the incidence of spontaneous abortion or preterm delivery.
To date, no racial predilection exists for ovarian germ cell tumors (GCTs).
These tumors mostly occur in women, although the disease also occurs in pseudohermaphrodites and patients with gonadal dysgenesis (see Complications). Testicular seminomas are the male histologic counterparts to dysgerminomas.
Although most ovarian cancers occur during the menopausal and perimenopausal years (ie, 50-59 y), dysgerminomas tend to occur frequently in the pediatric population. Dysgerminomas are most commonly observed in younger women. Seventy-five percent of dysgerminomas occur in patients in the third and fourth decades of life, with the mean age being 22 years.
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