40 Incidental Pelvic Mass


40 Incidental Pelvic Mass

Kaustubh G. Shiralkar, Eduardo J. Matta, Steven S. Chua, and Chakradhar R. Thupili

40.1 Case Presentation

A 39-year-old woman presented with lower back pain for which an MRI of the lumbar spine without intravenous (IV) contrast was performed (▶ Fig. 40.1).

Fig. 40.1 Sagittal T1-weighted image (a) and sagittal T2-weighted image (b) from a lumbar spine MRI without contrast.

40.2 Imaging Findings and Impression

The MRI images demonstrate an incidentally detected, partially visualized multilocular cystic left adnexal mass with slightly thickened septations (arrows in ▶ Fig. 40.1). The abnormality is at the edge of the field of view and incompletely characterized on this examination. Benign physiologic ovarian/corpus luteal cysts are the most common cystic lesions in young, premenopausal women. In this case, however, the size and presence of septations warrant further workup and complete imaging.

40.2.1 Additional Testing Needed

  • A pelvic ultrasound with transabdominal and transvaginal imaging is the first modality to work up a uterine or adnexal lesion (▶ Fig. 40.2).

  • Cross-sectional imaging with CT and/or MRI with contrast can also be utilized in more complex cases and for problem-solving if ultrasound is inconclusive.

Fig. 40.2 Sagittal transabdominal (TA) ultrasound image of the left adnexa (a), sagittal TA image with color of the left adnexa (b), and transverse transvaginal image (c).

40.2.2 Pelvic Ultrasound Findings and Impression

Pelvic ultrasound examination done approximately 12 weeks later demonstrates a 9-cm large multilocular cystic mass with thickened septations. No internal vascularity is demonstrated. Findings are concerning for cystic ovarian neoplasm; therefore, referral to gynecologist was made. Due to size (> 7 cm), persistence on follow-up imaging, and internal complexity, the lesion was excised.

Follow-up: The patient underwent a left oophorectomy and final pathology revealed a serous cystadenoma.

40.3 Essential Information regarding Ovarian Serous Cystadenomas

  • Ovarian serous cystadenoma is a benign lesion classified as epithelial ovarian neoplasm and often indistinguishable from functional ovarian cysts on imaging.

  • It can be encountered at any age, but peak incidence is typically in the fourth and fifth decades of life.

  • It accounts for 25% of all benign ovarian neoplasms and 10 to 20% are bilateral.

  • Key in distinguishing it from a physiologic ovarian cyst is its size (average of 10 cm) and persistence on follow-up examinations (most important differentiating factor).

  • It can be multilocular with septations, but will usually not have internal vascularity within the septation or solid component such as mural nodules. The best initial imaging tool for characterization is ultrasound (▶ Table 40.1).

Table 40.1 Differential diagnosis of commonly detected adnexal masses

Differential diagnosis


Physiologic ovarian/para-ovarian cyst

Thin wall with lack of complex features such as thick septations or mural nodules; a hemorrhagic cyst may mimic a solid lesion but usually resolves with short-term follow-up

Corpus luteal cyst

Characteristic rim enhancement or vascularity

Ovarian cystic neoplasm

Complex multilocular with solid mural nodules and septations; often will enhance


Solid or complex fluid density with nonspecific CT appearance; may have characteristic T2-“shading” and T1 bright signal due to intrinsic blood products on MR


May mimic ovarian cyst but tubular in shape and para-ovarian location

Dermoid cyst

Fat attenuation on CT and variable calcium; increased T1 and T2 signal with loss of signal on fat saturation images on MR due to macroscopic fat content

Uterine leiomyoma

Subserosal or pedunculated leiomyomas may mimic solid adnexal/ovarian lesions; Look for uterine origin on CT/MRI; Generally low T2 signal on MR and may have calcifications on CT.

Bowel loop

Use multiplanar reformats on CT or multiple planes on MR if available to differentiate from fluid-filled small bowel loops

Bladder diverticulum

Large bladder diverticulum or ureterocele can mimic a cystic adnexal lesion; look for connection to bladder or ureter

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Jun 28, 2020 | Posted by in NEUROLOGICAL IMAGING | Comments Off on 40 Incidental Pelvic Mass

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