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Incidentally Detected Adnexal Masses
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- Incidental adnexal masses are common in both pre- and postmenopausal women; the vast
majority are benign
- Ultrasound demonstrates high sensitivity but low specificity for detecting ovarian cancer. MRI
evaluation of adnexal masses indeterminate on ultrasound increases specificity, decreasing
resection of benign lesions
- An algorithm to evaluate adnexal masses with imaging is presented. The goal is to identify patients
with definitely benign lesions from those that require further clinical evaluation for ovarian cancer
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Ovarian
cancer is the leading cause of death from gynecological cancers, with
22,480 estimated new cases and 15,280 deaths in 2007. If it is
diagnosed at Stage I, there is an almost 90% survival rate at 5 years;
but if diagnosed at an advanced stage, as are most cases, the 5 year
survival rate is <30%. Several screening programs, undertaken
with the hope of detecting ovarian cancer at an early stage, have
provided valuable insight into the incidence of adnexal masses, their
natural history, and strategies for their management.
Natural History of Adnexal Masses
Screening
trials using imaging have proven unsuccessful because benign adnexal
lesions are relatively common whereas ovarian cancer is rare. In
one study following >15,000 asymptomatic postmenopausal women over
an average period of 6.3 years, 18% developed unilocular cysts of which
69% resolved spontaneously. In the 10 women diagnosed with ovarian
cancer, the cysts either developed complex features, resolved before
diagnosis, or the cancer developed in the contralateral ovary. The risk
of cancer eventually developing from a unilocular cyst was calculated
to be <0.1%. Complex ovarian cysts show a reported incidence of 3.2%
in postmenopausal women 55% of which resolve within 60 days.
Screening trials have also revealed that the majority of ovarian
cancers demonstrate very rapid growth. In one study, the
frequency of ovarian cancer in women with persistent complex cysts was
6.1% and all but one grew during the 4-6 week period between initial
detection and follow-up scanning. In another, in which women were
examined every 6 months with transvaginal ultrasound, all 10 of the
ovarian cancers detected were at advanced stage (III or IV), having
developed within the 6 month interval between screenings. From this,
the authors estimated a tumor volume doubling time for ovarian cancer
of <3 months and concluded that periodic imaging is ineffective in
early detection.
Incidental Adnexal Lesion Seen in Imaging
An
algorithm for the use of imaging for the evaluation of incidentally
detected adnexal masses is shown in Figure 1. An adnexal lesion
found incidentally, usually on CT or ultrasound examination, does not
need further imaging characterization if it is obviously malignant,
e.g. concurrent omental implants, other evidence of peritoneal
disseminated disease, or lymphadenopathy. In addition, simple cysts
less than 5-6 cm, with no solid components in a premenopausal woman,
are likely benign and do not require further imaging. (Simple cysts
that are larger may warrant additional imaging to document resolution
as these cysts can torse and may need to be removed surgically if they
persist). On the other hand, lesions found in postmenopausal
women and those that have solid components require further evaluation. |
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| Table 1. Incidence of Ovarian Cysts |
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Ovarian cyst
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Estimated Prevalence
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Risk of Malignancy
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Unilocular Ovarian Cyst
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Postmenopausal,
<10 cm: 3-18%
Postmenopausal,
>2.5 cm: 6.4%
Premenopausal,
>2.5 cm: 12.6%
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0 - 0.1%
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Complex Ovarian Cyst
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Postmenopausal, 3.2%
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3%
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For
this purpose, follow-up imaging (usually within 6 weeks) is recommended
either with ultrasound or MRI. Adnexal lesions can be
definitively characterized as benign if they demonstrate specific
imaging features or if they resolve on follow-up imaging. If not
definitely benign on follow-up, the patient should be evaluated
clinically to exclude the possibility of ovarian cancer.
Clinical
evaluation for ovarian cancer includes medical and family history,
physical exam and serum CA-125 levels which, in combination with
imaging findings, determine the index of suspicion and guide referral
to a gynecologic oncologist. Neither imaging results (Table 2) nor
CA-125 levels alone are sufficiently accurate to diagnose ovarian
cancer. CA-125 is elevated in 90% of women with advanced ovarian
cancer but only in 50% of those diagnosed with stage I disease. In
addition, CA-125 elevation is associated with many other benign
conditions, including pregnancy, leiomyomas, liver or kidney disease,
pelvic inflammatory disease, endometriosis, and benign ovarian tumors.
Because of the observed rapid doubling time for ovarian cancer, if
imaging cannot quickly characterize an ovarian lesion as benign, or if
clinical indicators (e.g. CA-125 levels) or patient risk factors, (e.g.
family history or genetic markers) suggest cancer, current
recommendations are that the lesion should be resected rather than
followed .
Because all these indicators even in combination are nonspecific,
surgical removal is >3 times more likely to yield a benign mass than
a cancer.
| Table 2. Diagnosis of Ovarian Malignancy with Imaging for Asymptomatic Adnexal Masses |
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Modality
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Sensitivity
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Specificity
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| Trans Vaginal Ultrasound (TVUS) |
92 |
60 |
| MRI |
83†
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84†
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| MRI after indeterminate US* |
81 |
98 |
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Data from McDonald and Modesitt, 2006
*Includes both asymptomatic and symptomatic masses.
† MRI sensitivity and specificity, 96.6 and 83.7, respectively, in
study of women with clinically suspected adnexal masses.
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| Figure 1. An algorithm for incidental adnexal mass evaluation |
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*If
CA-125 elevated, refer to gynecologic oncologist. If CA-125 normal,
refer to general gynecologist or gynecologic oncologist based on
clinical assessment of risk for ovarian cancer.
†May need evaluation by gynecologist if sympomatic or large size (>5-6 cm) could cause torsion
‡Suspect endometrioma, dermoid, fibroma, exophytic fibroid, or peritoneal inclusion cyst
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Ultrasound Characterization of Adnexal Masses
Incidental
adnexal masses represent a wide variety of pathologies including
functional cysts, sequelae of prior infection, endometriosis, benign or
malignant neoplasms, and those originating from adjacent pelvic organs.
The goal of imaging is to differentiate between benign and malignant
disease. Transvaginal ultrasound (TVUS) is the preferred method for
initial evaluation. It is usually combined with transabdominal
ultrasound, which may be necessary to detect both ovaries and can
detect ancillary features of malignancy such as hydronephrosis,
ascites, and pleural effusions.
Ultrasound features of a
benign mass (Figure 2) are a simple unilocular cyst with a thin smooth
wall. Complex cysts with hyperechoic regions may indicate a dermoid,
and cysts with uniform hypoechoic texture can suggest
endometriomas. These are benign lesions, which when suspected on
ultrasound, are often referred for definitive characterization with MRI
(Figure 2). Because ultrasound features suggesting a benign lesion are
well understood, the reported negative predictive value of ultrasound
for malignancy is high at 98%.
Features suggestive of malignancy include that of a complex cyst
(Figure 3) with thickened walls, septations, papillary solid components
and flow detected on Doppler. However, because many physiologic cysts
and benign tumors have similar characteristics to malignancy,
specificity of ultrasound for ovarian cancer is low (Table 2).
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Figure 2. Benign Cyst
- Transvaginal ultrasound image of the right adnexa in this
postmenopausal patient reveals a 2.0 cm simple unilocular
cyst. This completely resolved on follow-up imaging in 3 months.
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| Figure 3. Ovarian Cancer - Transvaginal
ultrasound image of the pelvis (A) demonstrates a large complex cystic
mass (arrows). Transabdominal ultrasound image of the upper
abdomen (B) demonstrates ascites (arrow) around the liver. |
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MRI Characterization of Adnexal Masses
MRI reduces the number of surgeries on benign adnexal lesions by
definitively characterizing them in selected cases. Adnexal lesions
with ultrasound features suggesting an endometrioma, dermoid, or an
extra-ovarian lesion (e.g. hydrosalpinx, peritoneal inclusion cyst,
peritubal cyst), or those appearing homogeneously solid (ovarian
fibroma or exophytic uterine or broad ligament fibroid) are further
characterized by MRI. However, MRI is usually not helpful for
characterizing many complex cystic intra-ovarian masses. When
ovarian lesions that are indeterminate on ultrasound are then examined
with contrast enhanced MRI, the sensitivity and specificity of the
combined examinations for ovarian cancer are 81% and 98%.
Scheduling
Ultrasound can be performed at all MGH imaging facilities and MRI can
be performed at Mass General Imaging in Waltham, Mass General Imaging
Chelsea, or the main MGH campus. These studies can be ordered online
via the Radiology Order Entry (http://mghroe
) or by calling 4-XRAY (617-724-9729).
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Further Information
For further questions on imaging of adnexal masses, please contact
, Staff Radiologist in the Abdominal Imaging and
Intervention Division at 617-726-8396.
We would like to thank Neil S. Horowitz, M.D., Gynecological
Oncologist, for his advice and assistance in the preparation of this
article.
This article provided useful information about the appropriate use of imaging studies:
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References
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ACOG Committee on Gynecologic Practice. (2002) The role of the generalist obstetrician-gynecologist in the early detection of ovarian cancer. Gynecol Oncol 87: 237-9
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McDonald, JM and Modesitt, SC. (2006) The incidental postmenopausal adnexal mass. Clin Obstet Gynecol 49: 506-16
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