Ovarian Masses Part 1

Review of ovarian masses for radiology board exams. After all episodes on this topic are posted, a free study guide will be available by clicking here.

Show Notes/Study Guide:

What are key imaging features of a hemorrhagic cyst?

A hemorrhagic ovarian cyst occurs when the granulosa layer within a corpus luteum ruptures and bleeds.  This is a common cause of acute onset pelvic pain although hemorrhagic cysts may also be asymptomatic. On ultrasound, the appearance can vary based on the age of blood products.  Typical features on ultrasound include what has been termed lace-like reticular echoes within the cyst and typical posterior acoustic enhancement and lack of internal blood flow on color Doppler imaging.  Alternatively, an intracystic clot with no internal blood flow may also be seen.  Fluid-fluid levels are sometimes seen internally. 

On MRI, one would expect a hemorrhagic cyst to be an adnexal mass with no internal enhancement, most commonly showing increased T1 and T2 signal. 

When might a hemorrhagic cyst require follow-up?

If on the Core Exam an ovarian cyst with features of a hemorrhagic cyst is greater than 5 cm in diameter if premenopausal, or of any size if postmenopausal, follow-up in 6-12 weeks with ultrasound or MRI is the best answer.  Most hemorrhagic cysts resolve within about 8 weeks so follow-up can help distinguish between a benign hemorrhagic cyst, or another process.

What are key imaging features of an endometrioma?

Endometriomas are the result of endometriosis of the ovaries with repeated bleeding of the endometrial tissues.  Clinical symptoms of an endometrioma can include pain as well as infertility which can occur in at least 25% of cases.  I usually think of an endometrioma as an ovary-specific process but technically these can occur elsewhere in the pelvis such as the pelvic cul-de-sac or broad ligament.

On ultrasound, a cyst with homogeneous echoes and posterior acoustic enhancement may be most classic but the ultrasound appearance is variable and can less commonly include multiple internal loculations, fluid-fluid levels, and a cystic and solid appearance. 

MRI has the shading sign on T2 that is something you should know about. Look this up if you don’t know what this looks like. Expect T1 hyperintensity, and low T2 signal in portions or the entirety of the cyst because of the recurrent hemorrhage with deposition of iron within the cyst.  In some cases, near complete loss of T2 signal may be seen. A hemorrhagic cyst would be expected to be brighter on T2 in classic cases compared to an endometrioma which shows variable degrees of T2 shading.

An endometrioma may show wall enhancement on MRI but any enhancing mural nodule or mass raises concern for a malignant lesion.

Is follow-up indicated for an endometrioma?

For the Core Exam, I would recommend choosing either surgical excision or annual follow-up for an endometrioma given a small risk of malignant transformation. Therapy with a gonadotropin-releasing hormone agonist may also be considered. 

What is the most common ovarian neoplasm in an adolescent?

Cystic ovarian teratomas which account for over 90% of ovarian neoplasms in this age range. Remember the large majority of these will be benign (about 90%), there is a risk of ovarian torsion which may be the presenting feature. In about 10-15% of cases these can be bilateral.

What are key features of an ovarian dermoid cyst?

A dermoid cyst of the ovary, at least for the Core Exam, is essentially the same as a mature cystic teratoma. It is important to remember that these contain tissue from multiple germ cell layers. Technically a dermoid has dermal and epidermal components whereas a teratoma has dermal, epidermal, mesodermal, and endodermal components, but that is likely beyond what is commonly tested on the Core Exam. These are bilateral in something like 10-15% of cases.

On radiography, an ovarian dermoid may manifest as adnexal calcifications due to components of teeth and bone in the mass.  On ultrasound, a dermoid cyst may demonstrate posterior acoustic shadowing and may show echogenic interfaces from bone that obscure underlying tissues termed the tip of the iceberg sign.  A Rokitansky nodule is a mural nodule that is frequently hyperechoic. Fluid-fluid levels can be seen.  Internal echogenic bands can be a manifestation of hair contained within the cyst. No internal vascularity is expected on color Doppler imaging.

CT will often show an adnexal mass containing internal fat, calcification/ossification, and possible fat-fluid levels.

MRI shows an adnexal mass with internal fat which can be confirmed by fat suppression and or chemical shift due to microscopic internal fat.  Solid components may show enhancement and raise concern for potential malignant transformation. 

What are some of the signs of ovarian dermoid cyst rupture?

Fat and fatty fluid can be seen in anti-dependent spaces in the abdomen and pelvis following rupture of an ovarian dermoid cyst including below the right diaphragm which is a classic location for this finding. Clinical symptoms from a chemical peritonitis are common.

What is typical management of an ovarian dermoid cyst?

If larger than something like 7 cm, surgery is often indicated. If under 7 cm, 12-month follow-up may be performed to document stability or identify need for surgery if the mass significantly enlarges. These can be very large (>10 cm) at presentation.

A struma ovarii tumor of the ovary contains tissue from what non-pelvic organ?

Struma ovarii contains thyroid tissue. This is in the family of ovarian teratomas and is often composed completely or majority of thyroid tissue (at least 50% thyroid tissue may be necessary for diagnosis) with internal colloid material. In up to about 10% of cases clinical hyperthyroidism may be present.

These cannot be differentiated on imaging from other ovarian neoplasms.

On MRI these often show heterogeneous signal intensity on both T1 and T2 weighted images and solid portions may show enhancement. 

These are mostly benign tumors that are often treated with surgical resection.

What are guidelines for ovarian cyst follow-up based on size of the cyst?

For pre-menopausal patients:

Cysts at or under 3 cm may be considered physiologic such as a corpus luteum or ovarian follicle and require no specific follow-up.

If over 3 cm in size, but equal or less than 5 cm, and demonstrating a simple appearance, no follow-up is necessary, but these should generally be reported in the imaging report.

If over 5 cm some form of follow-up is generally needed which initially is often in the range of 2-6 months to see if it resolves, and subsequently, if not resolved or decreased in size, every 6 to 12 months to ensure stability.

For post-menopausal patients criteria are stricter and follow-up is generally needed for cysts that are over 3 cm in size, initially at 2-6 months for resolution and then every 6-12 months if similar in size.

Generally, 2 years of stability for larger cysts requiring follow-up per the criteria discussed is necessary before they may be considered benign, especially on the Core Exam.

If cysts are large or increase in size, surgery may be performed for resection and definitive characterization.

What are findings of ovarian hyperstimulation syndrome?

Often related to ovarian induction therapy for in vitro fertilization, this manifests as ovarian enlargement with some degree of fluid accumulation in the abdomen and pelvis that may include ascites and pleural effusions. Ultrasound shows bilateral symmetric enlargement of ovaries that may become very large such as over 10 cm in size with multiple internal cysts that sometimes show a spoke-wheel appearance.

Clinical symptoms include acute pelvic pain, abdominal distention, and in severe cases, hemodynamic instability from fluid shift and third spacing of large amounts of fluid.

This is more common in younger patients.