Carcinoma that appears predominantly as peritoneal carcinomatosis without appreciable ovarian or fallopian tube enlargement is called peritoneal carcinoma or m¨ullerian carcinoma when tumors spread from the breast, gastrointestinal tract, and other organs of nonm¨ullerian origin are excluded. Most are peritoneal serous carcinomas, which have the appearance of a moderately to poorly differentiated serous ovarian carcinoma. Peritoneal endometrioid carcinoma is less common.
Peritoneal carcinoma should be considered clinically the same as ovarian and fallopian tube cancers. In patients for whom exploratory surgery is performed, there may be microscopic or small macroscopic cancer on the surface of the ovary and extensive disease in the upper abdomen, particularly in the omentum (28).
Mesotheliomas Peritoneal malignant mesotheliomas may be epithelial, sarcomatous, or biphasic (2,29). Deciduoid peritoneal mesothelioma is an unusual variant that resembles exuberant, ectopic decidual reaction of the peritoneum. Asbestos exposure is not correlated with peritoneal mesotheliomas in women. These lesions typically appear as multiple intraperitoneal masses, often coating the entire peritoneum and can develop after hysterectomy and bilateral salpingo-oophorectomy for benign disease. Malignant mesotheliomas should be distinguished from benign multicystic peritoneal mesothelioma (multilocular peritoneal inclusion cyst), and ovarian tumor implants and primary peritoneal m¨ullerian neoplasms.
Clinical Features More than 80% of epithelial ovarian cancers are found in postmenopausal women (Fig. 37.8). The peak incidence of invasive epithelial ovarian cancer is at 56 to 60 years of age (2,3,30). The age-specific incidence of ovarian epithelial cancer rises precipitously from 20 to 80 years of age and subsequently declines (30). These cancers are relatively uncommon in women younger than age 45. Fewer than 1% of epithelial ovarian cancers occur before the age of 21 years, two-thirds of ovarian malignancies in such patients being germ cell tumors (2,30,31). About 30% of ovarian neoplasms in postmenopausal women are malignant, whereas only about 7% of ovarian epithelial tumors in premenopausal patients are frankly malignant (2,3).
The average age of patients with borderline tumors is approximately 46 years (2,3,9). Eighty percent to 90% of ovarian cancers, including borderline forms, occur after the age of 40 years, whereas 30% to 40% of malignancies occur after the age of 65 years. The chance that a primary epithelial tumor will be of borderline or invasive malignancy in a patient younger than 40 years is approximately 1 in 10, but after that age it rises to 1 in 3 (2,3). Less than 1% of epithelial ovarian cancers occur before the age of 20 years, with two-thirds of ovarian malignancies in such patients being germ cell tumors (31).
Etiology Ovarian cancer is associated with low parity and infertility (32). Although there are a variety of epidemiologic variables correlated with ovarian cancer, such as talc use, galactose consumption, and tubal ligation (see Chapter 4), none is so strongly correlated as prior reproductive history