Ovarian Cancer (Epithelial)
Synonyms/Description
Ovarian carcinoma or adenocarcinoma
Etiology
Ovarian cancer is the second most common (endometrial is number one) genital tract malignancy (1% to 2% lifetime risk) and the most deadly (overall 5-year survival of 45%). Familial predisposition accounts for 5% to 10% of women who develop ovarian cancer and is typically associated with BRCA1 and BRCA2 gene mutations. Ovarian cancer is more prevalent with increasing age, usually occurring in postmenopausal women. Most cancers are of the epithelial type, the most common of these being serous cystadenocarcinoma (greater than 50%); the cell type comprising this tumor is very similar to that found in the fallopian tubes. Endometrioid adenocarcinoma (15% to 20% of epithelial ovarian cancers) and clear cell tumors of the ovary (6% of epithelial tumors) are associated with pelvic endometriosis and tend to occur in younger women. Mucinous adenocarcinoma (5% to 10% of epithelial tumors) is a mucin-producing tumor and resembles the intestinal or endocervical cell types. Other rarer cell types include carcinosarcoma (epithelial and mesenchymal mixed tumor), transitional cell, squamous cell carcinoma, and Brenner tumors (see related sections elsewhere in the book).
Traditionally, ovarian cancer was thought to arise de novo from the surface epithelium (mesothelium) of the ovary. However, there is recent evidence that the most common ovarian cancer originates from the fallopian tube. This precursor lesion, called serous intraepithelial tubal carcinoma (STIC), is very similar to high-grade ovarian serous carcinoma. The current theory is that most of these tumors arise from a STIC in the fimbriated end of the fallopian tube then spread to the ovary.
Even when the ovaries have been removed, a patient can still develop primary peritoneal carcinoma. This entity, known as serous surface papillary carcinoma of extra-ovarian origin, is considered a very aggressive cancer.
Ultrasound Findings
Pattern recognition and Doppler features of an ovarian mass are the most accurate method of differentiating a malignant from a benign tumor when performed by an experienced practitioner. In general, unilocular clear cysts with smooth borders, no nodularity, and absent internal blood flow are characteristic features of a benign mass. Papillary projections with abundant blood flow, large and irregular solid components, thick septations, and irregular walls are signs of malignancy. These features are characteristic of all epithelial ovarian tumors; hence, it is not possible to distinguish the exact tissue diagnosis sonographically. Once the tumor is advanced, ascites and peritoneal seeding are common and easily visualized sonographically.
Color flow Doppler is very important to evaluate the presence or absence of prominent vessels within the solid areas of the tumor. Prior reports suggested that spectral Doppler indices might be helpful to distinguish malignant from benign lesions. Although vessels in a malignant mass have a lower resistive index and abundant diastolic flow compared with those seen in benign masses, this finding has not been helpful in premenopausal women. The corpus luteum is very vascular with a low resistive pattern similar to tumor vessels, making the spectral Doppler waveform potentially useful only in postmenopausal patients. The mapping of blood vessels in the center of a mass is far more informative than the spectral Doppler waveform. More recently, some authors have suggested using 3-D ultrasound with power Doppler to quantify the blood flow within the solid portions of the tumor. Three-dimensional power Doppler vascular indices used to quantify blood flow include the vascularization index, flow index, and vascularization-flow index. Although evaluating the blood flow indices within a mass may be of some value, it does not seem to add substantially to the subjective sonographic assessment of the mass by experienced practitioners.
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