Ovarian masses are common in women of all ages. It is important not to miss even one ovarian cancer, but we must also identify masses that will resolve on their own over time to avoid overtreatment. These concurrent goals of excluding malignancy while not overtreating patients are the basis for management of the pelvic mass. Additionally, fertility preservation is important when surgery is performed in a reproductive-aged woman.
An ovarian mass may be anything from a simple functional or physiologic cyst to an endometrioma to an epithelial carcinoma, a germ-cell tumor, or a stromal tumor (the latter three of which may metastasize). Across the general population, women have a 5%-10% lifetime risk of needing surgery for a suspected ovarian mass and a 1.4% (1 in 70) risk that this mass is cancerous. The majority of ovarian cysts or masses therefore are benign.
A thorough history – including family history – and physical examination with appropriate laboratory testing and directed imaging are important first steps for the ob.gyn. Fortunately, we have guidelines and criteria governing not only when observation or surgery is warranted but also when patients should be referred to a gynecologic oncologist. By following these guidelines,1 we are able to achieve the best outcomes.
Transvaginal ultrasound
A 2007 groundbreaking study led by Barbara Goff, MD, demonstrated that there are warning signs for ovarian cancer – symptoms that are significantly associated with malignancy. Dr. Goff and her coinvestigators evaluated the charts of hundreds of patients, including about 150 with ovarian cancer, and found that pelvic/abdominal pressure or pain, bloating, increase in abdominal size, and difficulty eating or feeling full were significantly and independently associated with cancer if these symptoms were present for less than a year and occurred at least 12 times per month.2
A pelvic examination is an integral part of evaluating every patient who has such concerns. That said, pelvic exams have limited ability to identify adnexal masses, especially in women who are obese – and that’s where imaging becomes especially important.
Masses generally can be considered simple or complex based on their appearance. A simple cyst is fluid-filled with thin, smooth walls and the absence of solid components or septations; it is significantly more likely to resolve on its own and is less likely to imply malignancy than a complex cyst, especially in a premenopausal woman. A complex cyst is multiseptated and/or solid – possibly with papillary projections – and is more concerning, especially if there is increased, new vascularity. Making this distinction helps us determine the risk of malignancy.
Transvaginal ultrasound (TVUS) is the preferred method for imaging, and our threshold for obtaining a TVUS should be very low. Women who have symptoms or concerns that can’t be attributed to a particular condition, and women in whom a mass can be palpated (even if asymptomatic) should have a TVUS. The imaging modality is cost effective and well tolerated by patients, does not expose the patient to ionizing radiation, and should generally be considered first-line imaging.3,4
Size is not predictive of malignancy, but it is important for determining whether surgery is warranted. In our experience, a mass of 8-10 cm or larger on TVUS is at risk of torsion and is unlikely to resolve on its own, even in a premenopausal woman. While large masses generally require surgery, patients of any age who have simple cysts smaller than 8-10 cm generally can be followed with serial exams and ultrasound; spontaneous regression is common.
Doppler ultrasonography is useful for evaluating blood flow in and around an ovarian mass and can be helpful for confirming suspected characteristics of a mass.
Recent studies from the radiology community have looked at the utility of the resistive index – a measure of the impedance and velocity of blood flow – as a predictor of ovarian malignancy. However, we caution against using Doppler to determine whether a mass is benign or malignant, or to determine the necessity of surgery. An abnormal ovary may have what is considered to be a normal resistive index, and the resistive index of a normal ovary may fall within the abnormal range. Doppler flow can be helpful, but it must be combined with other predictive features, like solid components with flow or papillary projections within a cyst, to define a decision about surgery.4,5
Magnetic resonance imaging can be useful in differentiating a fibroid from an ovarian mass, and a CT scan can be helpful in looking for disseminated disease when ovarian cancer is suspected based on ultrasound imaging, physical and history, and serum markers. A CT is useful, for instance, in a patient whose ovary is distended with ascites or who has upper abdominal complaints and a complex cyst. CT, PET, and MRI are not recommended in the initial evaluation of an ovarian mass.