Figure 37.18 Dysgerminoma of the ovary. Note that the lesion is principally solid with some cystic areas and necrosis.
to 3% of all ovarian cancers, but they represent as many as 5% to 10% of ovarian cancers in patients younger than 20 years. Seventy-five percent of dysgerminomas occur between the ages of 10 and 30 years, 5% occur before the age of 10 years, and they rarely occur after 50 years of age (2,3,336). Because these malignancies occur in young women, 20% to 30% of ovarian malignancies associated with pregnancy are dysgerminomas.
Germinomas are found in both sexes and may arise in gonadal or extragonadal sites.
The latter include the midline structures from the pineal gland to the mediastinum and the retroperitoneum. Histologically, they represent abnormal proliferations of the basic germ cell. In the ovary, the germ cells are encapsulated at birth (the primordial follicle), and the unencapsulated or free cells die. If either of the latter processes fails, it is possible that the germ cell could free itself of its normal control and multiply indiscriminately.
The size of dysgerminomas varies widely, but they are usually 5 to 15 cm in diameter (2,3). The capsule is slightly bosselated, and the consistency of the cut surface is ﬂeshy and pale tan to gray-brown in color (Fig. 37.18).
The histologic characteristics of the dysgerminoma are very distinctive. The large round, ovoid, or polygonal cells have abundant, clear, very-pale–staining cytoplasm, large and irregular nuclei, and prominent nucleoli (Fig. 37.19). Mitotic figures are seen in varying numbers, although they are usually numerous. Another characteristic feature is the arrangement of the elements in lobules and nests separated by fibrous septa, which are often extensively infiltrated with lymphocytes, plasma cells, and granulomas with epithelioid cells and multinucleated giant cells. When necrosis is extensive, the lesion may be confused with tuberculosis. Dysgerminomas may contain syncytiotrophoblastic giant cells and may be associated with precocious puberty or virilization. The presence of these cells does not seem to alter the behavior of the
Figure 37.19 Dysgerminoma of ovary. Primitive germ cells are divided into clusters and lobules by fibrous septa rich in lymphocytes.
tumor (2,3). The presence of calcifications should prompt a search for a possible underlying gonadoblastoma.
Because the dysgerminoma is a germ cell tumor and parthenogenesis (stimulation of the basic germ cell to atypical division) is the accepted genesis for the more immature teratomas, it is logical that these two tumors may coexist. Choriocarcinoma, endodermal sinus tumor, and other extraembryonal lesions may be associated with the dysgerminoma.
Approximately 5% of dysgerminomas are discovered in phenotypic women with abnormal gonads (2,349,351). This malignancy can be associated with patients who have pure gonadal dysgenesis (46,XY, bilateral streak gonads), mixed gonadal dysgenesis (45,X/46,XY, unilateral streak gonad, contralateral testis), and the androgen insensitivity syndrome (46,XY, testicular feminization). For premenarcheal patients with a pelvic mass, the karyotype should be determined (see Chapter 29).