Ovarian cancer mimics: how to avoid being fooled by extraovarian pelvic masses

Imaging of a Pelvic Mass: Uterine

The most common origin of a non-uterine pelvic mass is from the ovary. Ultrasound is the initial imaging modality of choice, additional imaging with computed tomography (CT) and/or magnetic resonance imaging (MRI) is performed in selected cases. Adnexal masses are also encountered as incidental findings during ultrasound, CT or MRI. Many of the adnexal masses that are surgically removed are benign. For optimal outcome and cost effective management, noninvasive risk stratification of such adnexal masses is necessary when discovered incidentally or when identified in a patient with a clinically detected pelvic mass. The American College of Radiology Ovarian-Adnexal Reporting Data System is a pattern-based scoring system for adnexal masses imaged with ultrasound and MRI, which assists clinicians to guide in the appropriate management based on evidence-based risk categories. Non-ovarian and non-uterine pelvic masses include fallopian tube abnormalities, paraovarian cysts, peritoneal inclusion cysts, and rare causes include masses that arise from the gastrointestinal tract or the sacrum. To distinguish non-ovarian masses from an ovarian tumor, a critical step is to identify a normal appearing ovary separate from the pelvic mass. This may be challenging in the post-menopausal woman with an atrophic ovary. MRI is a useful adjunctive modality in such cases. Extraovarian masses typically displace pelvic side wall vasculature medially, compress, encase or medially displace the ureters.

Diffusion-weighted magnetic resonance sequence and CA125/CEA ratio can be used as add-on tools to ultrasound for the differentiation of ovarian from non-ovarian pelvic masses

OBJECTIVE

To provide a straightforward approach to the sequential use of ultrasound (US), magnetic resonance (MR) and serum biomarkers in order to differentiate the origin of pelvic masses, making the most efficient use of these diagnostic resources.

STUDY DESIGN

This is a cross-sectional study with 159 patients (133 with ovarian and 26 with non-ovarian tumors) who underwent surgery/biopsy for an adnexal mass. Preoperative CA125 and CEA serum measurements were obtained and a pelvic/abdominal ultrasound was performed. Preoperative pelvic MR studies were performed for all patients. Morphological and advanced MR sequences were obtained. Using a recursive partitioning algorithm to predict tumor origin, we devised a roadmap to determine the probability of non-ovarian origin using only statistically significant US, laboratory and MR parameters.

RESULTS

Upfront US classification as ovarian versus non-ovarian and CA125/CEA ratio were significantly associated with non-ovarian tumors. Signal diffusion (absent/low versus high) was the only MR parameter significantly associated with non-ovarian tumors. When upfront US designated a tumor as being of ovarian origin, further MR signal diffusion and CA125/CEA ratio were corrected nearly all US errors: patients with MR signal diffusion low/absent and those with signal high but CA125/CEA ratio ≥25 had an extremely low chance (<1%) of being of non-ovarian origin. However, for women whose ovarian tumors were incorrectly rendered as non-ovarian by upfront US, neither MR nor CA125/CEA ratio were able to determine tumor origin precisely.

CONCLUSION

MR signal diffusion is an extremely useful MR parameter to help determine adnexal mass origin when US and laboratory findings are inconclusive.

Nonovarian Mimics of Ovarian Malignancy

Once a pelvic mass is identified on an ultrasound examination, the first step in the differential diagnostic work up is to determine its origin. Most lateral pelvic masses in women are ovarian in origin, and the distinction between ovarian and nonovarian mimics of ovarian cancer is critical for appropriate clinical and surgical management. Adnexal masses detected on ultrasound can be further characterized by magnetic resonance imaging (MRI) when needed. Superior contrast resolution, multiplanar imaging, characteristic signal intensity of common pathology such as dermoid tumors or endometriomas allows one to accurately evaluate adnexal tumors with supplemental use of MRI. Commonly encountered extraovarian abnormalities that mimic ovarian malignancies are categorized as being either predominantly cystic or solid. The common causes of such extraovarian lesions that mimic ovarian pathology include fallopian tube diseases, paroaovarian cysts, peritoneal inclusion cysts, and a pedunculated or a broad ligament fibroid. Less common causes of cystic and solid nonovarian mimics of ovarian malignancy include mucocele of the appendix, lymphocele, spinal meningeal cysts, extraovarian endometriomas, extraovarian fibrothecomas, and gastrointestinal stromal tumors (Table 1). Identifying a normal appearing ovary is the key in distinguishing an extraovarian pelvic mass from an ovarian tumor. This becomes particularly challenging in postmenopausal women with atrophic ovaries. In this scenario, MRI comes into use by identifying small atrophic ovaries more often than ultrasound is able to. Extraovarian lesions typically displace the pelvic sidewall vasculature medially, ureters tend to be compressed, encased or medially displaced, enhancement matches pelvic arteries and may be associated with engorged mesenteric vessels compared to gonadal vessel engorgement seen with ovarian tumors.