These tumors may be solid or cystic; they sometimes develop in association with endometriosis. On microscopic examination, they are distinguished by the formation of tubular glands, similar to those of the endometrium, within the lining of cystic spaces. Although benign and borderline forms exist, endometrioid tumors usually are malignant. They are bilateral in about 30% of cases, and 15% to 30% of women with these ovarian tumors have a concomitant endometrial carcinoma. Similar to endometrioid-type carcinoma of the endometrium, endometrioid carcinomas of the ovary frequently have mutations in the PTEN tumor suppressor gene as well as mutations in other genes that also act by upregulating PI3K-AKT signaling.
The Brenner tumor is an uncommon, solid, usually unilateral ovarian tumor consisting of abundant stroma containing nests of transitional-type epithelium resembling that of the urinary tract. Occasionally, the nests are cystic and are lined by columnar mucus-secreting cells. Brenner tumors generally are smoothly encapsulated and gray-white on cut section, ranging from a few centimeters to 20 cm in diameter. These tumors may arise from the surface epithelium or from urogenital epithelium trapped within the germinal ridge. Although most are benign, both malignant and borderline tumors have been described.
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Fig.19.17Ovarianmucinouscystadenoma.(A)Mucinouscystadenomawithmulticysticappearanceanddelicatesepta.Notethepresenceofglisteningmucinwithinthecysts.(B)Columnarcellliningofmucinouscystadenoma.
Many other types of tumors of germ cell and sex cord– stromal origin also arise in the ovary, but only the teratomas of germ cell origin are sufficiently common to merit description.
Table 19.4 presents some salient features of other neoplasms of germ cell and sex cord origin.
Teratomas constitute 15% to 20% of ovarian tumors. A distressing feature of these germ cell tumors is their predilection to arise in the first 2 decades of life; to make matters worse, the younger the person, the greater the likelihood of malignancy. More than 90% of these germ cell neoplasms, however, are benign mature cystic teratomas; the immature, malignant variant is rare.
Benign (mature) cystic teratomas are marked by the presence of mature tissues derived from all three germ cell layers: ectoderm, endoderm, and mesoderm. Usually these tumors contain cysts lined by epidermis replete with adnexal appendages—hence the common designation dermoid cysts. Most are discovered in young women as ovarian masses or are found incidentally on abdominal radiographs or scans because they contain foci of calcification produced by toothlike structures contained within the tumor. About 90% are unilateral, with the right side more commonly affected. Rarely do these cystic masses exceed 10 cm in diameter. On cut section, they often are filled with sebaceous secretion and matted hair that, when removed, reveal a hair-bearing epidermal lining (
Fig. 19.18 ). Sometimes there is a nodular projection from which teeth protrude. Occasionally, foci of bone and cartilage, nests of bronchial or gastrointestinal epithelium, or other tissues are present.
For unknown reasons, these neoplasms sometimes produce infertility and are prone to undergo torsion (in 10%–15% of cases), which constitutes an acute surgical emergency. A rare, but fascinating, paraneoplastic complication is limbic encephalitis, which may develop in women with teratomas containing mature neural tissue and often remits with tumor resection. Malignant transformation, usually to a squamous cell carcinoma, is seen in about 1% of cases.