Although no sonologist can make a definitive diagnosis in every case of clinically suspected ovarian pathology, hallmark characteristics of an ovarian mass contribute greatly to the clinician’s appraisal of a tumor’s malignant potential.
Ultrasound reveals details about the size and architecture of ovarian masses that are indispensable in the initial evaluation of clinically suspect ovarian pathology. Nevertheless, determining whether a mass requires surgery remains a formidable challenge, thanks to the variability in the macroscopic characteristics of benign and malignant lesions. The task is further complicated by the diversity among ovarian tumors, which can be classified into 35 subtypes.1
Here, I present a systematic approach to investigating an ovarian mass via ultrasound, focusing on 9 key questions. The morphologic criteria outlined in this article provide the basis for distinguishing between benign and potentially malignant lesions, with a high probability of success.
Keep in mind: Ultrasound cannot provide histologic information. This limitation is important because several types of ovarian masses can have a similar sonographic appearance. The endpoint should be whether or not a specific patient requires surgical intervention.
Whether a patient should be referred to a subspecialist depends on the gynecologist’s level of experience as well as the sonographic criteria.
Evaluate ovarian cancer risk
The first step in evaluating an ovarian mass, prior to ultrasound examination, is to estimate the likelihood of malignancy. In the general population, the risk of ovarian cancer is 1 in 55 (1.8%),2 but certain factors may increase this risk:
- Age. In women with adnexal masses, those 60 to 69 years of age have 12 times the malignancy risk of those aged 20 to 29.3
- Family history. Five percent of women with ovarian cancer have a family history of the disease.4 The lifetime risk of ovarian cancer based on family history alone ranges from 6.7% for 1 first-degree relative with the disease to 40% for women with hereditary syndrome (TABLE 1).5,6 Ovarian cancer risk is not increased in the relatives of women with borderline tumors.5 When ovarian cancer has an autosomal dominant inheritance pattern, the age of onset is progressively younger by 10 to 15 years in each generation.7
On the other hand, the use of oral contraceptives for 5 years has been found to reduce the lifetime risk of ovarian cancer in the general population to 0.8%.8
Lifetime risk of ovarian cancer
|1 first-degree relative||6.7|
|2 to 3 first-degree relatives||8.2|
|Data from: Schildkraut and Thompson5 and NIH Consensus Panel6|
Transabdominal versus transvaginal views
Transabdominal sonography provides an overview of the pelvis and permits evaluation of masses beyond the field of view of the transvaginal transducer.
In contrast, the transvaginal approach permits utilization of higher-frequency transducers, offering superior resolution.
Transvaginal sonography yields the greatest amount of information when used as an extension of a thorough pelvic examination. During real-time scanning, an examiner can optimize visualization of some adnexal masses by placing pressure on the transvaginal probe and on the patient’s abdomen with his or her free hand. Such examination may elicit pelvic tenderness and helps the examiner assess the mobility and compressibility of an ovarian mass, as well as the consistency of its internal structures.
Question 1What is the size of the lesion?
The risk of malignancy increases with size, regardless of sonomorphology. In general, ovarian tumors larger than 10 cm are unsuitable for morphologic assessment. In most cases, the clinician would proceed to surgery.
For tumors smaller than 5 cm, morphology and Doppler studies may yield relevant information.
- What is the size of the lesion?
- Is the mass solid?
- Is it a simple or complex cyst?
- Is the cyst loculated?
- Are papillary excrescences present?
- Are there echo-dense foci?
- Is there echogenicity of interior fluid?
- Is measurable fluid in the cul-de-sac?
- How does the mass change over time?
The morphologic assessment of tumors between 5 and 10 cm should be considered on an individual basis. All the criteria outlined below help determine whether observation or surgery is best in a specific case. For example, a clear 7-cm cyst in an asymptomatic 21-year-old patient might best be observed.
TABLE 2 lists the positive predictive values of size from different series. Variation among them may be explained by a different prevalence of ovarian malignancy in each series.
Size as a predictor of malignancy in ovarian tumors
|AUTHOR||YEAR||POSITIVE PREDICTIVE VALUE OF TUMOR SIZE|
|<5 cm||5-10 cm||>10 cm|
Question 2 Is the mass solid?
When a solid adnexal mass is detected, the sonologist should consider the possibility of a pedunculated leiomyoma. A stalk with vascular flow from the mass to the main body of the uterus confirms this pathology; a normal ovary on that side excludes it.