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1 Department of Radiology, Massachusetts General Hospital, 55 Fruit St., White 270, Boston, MA 02114.
Received June 14, 2006;
accepted after revision June 16, 2006.
Address correspondence to S. I. Lee
(slee0{at}partners.org).
Abstract
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Keywords: adnexal masses • genitourinary tract imaging • MRI • reproductive organ imaging • sonography
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| QUESTION 1 Sonogram shows an adnexal lesion that is homogeneously solid. What lesion should NOT be included in the differential diagnosis?
QUESTION 2 Which MRI feature is NOT seen in benign endometrioma of the adnexa?
QUESTION 3 Which MRI pulse sequence is most sensitive in detecting pelvic endometriosis?
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Solution to Question 1
Fibroma is the most common sex cord stromal tumor of the ovary and
typically appears as a well-defined, hypoechoic mass on sonography
[1]. Endometriomas show a
spectrum of appearances on sonography, including a solid-appearing ovarian
lesion with diffuse low-level internal echoes
[2]. Dermoids manifest a
variety of appearances and, when small, can appear as homogeneously solid
echogenic ovarian masses [3].
Metastases to the ovary may appear as homogeneously solid masses. Peritoneal
inclusion cysts typically appear as loculated collections of fluid surrounding
but not obliterating an ovary
[4]. Although these cysts can
sometimes show solid components—for example, septations or mural
nodularity—they are predominantly cystic and are never homogeneously
solid. Option D is the best response.
| QUESTION 4 Which lesion generally requires histopathologic examination in order to make a definitive diagnosis?
QUESTION 5 A woman undergoes sonography to evaluate an adnexal mass. In which circumstance would further imaging by MRI be redundant and not contribute to management?
QUESTION 6 A sonographic examination reveals a 5-cm complex cyst with reticular thin septations in the right ovary of a premenopausal woman. What is the most appropriate next management step?
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Solution to Question 2
Endometriomas contain high concentrations of paramagnetic products of
hemoglobin breakdown. Consequently, they are intensely T1 hyperintense and
show no decrease in signal with fat-suppression pulse sequences
[5]. On T2-weighted images,
they can show the spectrum of signal intensities from hypointense to
hyperintense. Endometriomas with T1 hypo- or isointense components that
enhance with gadolinium should be regarded as suspicious for malignant
degeneration [6]. Benign
endometriomas should not show gadolinium enhancement. Option D is the best
response.
Solution to Question 3
Ovarian endometriomas and extraperitoneal endometriotic implants can show a
variety of appearances on MRI. However, extremely high T1 signal that is
homogeneously bright is considered diagnostic of an endometrioma and
endometriosis. Because they are "light-bulb" bright in the
surrounding dark pelvic soft tissue, endometriomas and endometriotic implants
are particularly easy to spot on fat-saturated T1-weighted images
[5]. Option B is the best
response. The conspicuity of endometriomas is decreased on T1-weighted
sequences without fat saturation, on which there is surrounding bright signal
from fat, and on gadolinium-enhanced T1-weighted sequences, on which normal
enhancing tissue and vessels appear bright. Endometriosis shows no
characteristic features on T2-weighted or inversion recovery sequences.
Solution to Question 4
Although they can show a spectrum of features, the characteristic
endometrioma is a well-defined, usually cystic lesion with diffuse low-level
internal echoes on sonography
[2] and is homogeneously
"light-bulb" bright on T1-weighted fat-saturated MR images
[5]. Peritoneal inclusion cysts
typically are loculated collections of fluid surrounding but not obliterating
the ovary [4]. Although benign
ovarian cystadenomas typically present as large (> 3 cm) complex cystic
masses with solid components—that is, with thick septations or mural
nodularity of papillary projections—they cannot be differentiated from
malignant ovarian tumors on imaging features alone. Option C is the best
response. Broad-ligament fibroids typically appear as completely solid
well-circumscribed adnexal masses separate from the ovary
[7]. Dermoids are characterized
by macroscopic fat that can be definitively characterized on MR
fat-suppression sequences.
Solution to Question 5
Simple unilocular cysts—cysts with an imperceptible wall and no solid
components—require no further imaging evaluation when presenting in a
premenopausal woman. Although they can rarely be a benign epithelial
tumor—for example, cystadenoma—they are usually physiologic
ovarian cysts or inclusion cysts and are not malignant
[8]. Option A is the best
response. Homogeneously solid masses on sonography could be further
characterized as a fibroma, endometrioma, or dermoid on MRI. Dermoids can
appear as cysts with regional bright echoes
[3] and acoustic shadowing, and
endometriomas can appear as cysts with diffuse low-level echoes and
hyperechoic wall foci [2].
Peritoneal inclusion cysts characteristically appear as multiloculated
collections of fluid surrounding an intact ovary. If sonographic findings are
equivocal, MRI can be helpful in more definitively characterizing all of these
lesions.
Solution to Question 6
The lesion described is characteristic of a hemorrhagic physiologic cyst
[9]. It should significantly
decrease in size or completely disappear on follow-up sonography after a
single menstrual cycle. Option A is the best response. Follow-up
imaging is necessary because this is a large (i.e., > 3-4 cm) mixed and
solid cystic ovarian lesion that cannot be distinguished from a malignancy
with complete certainty on a single imaging study. Although hemorrhagic cysts
can show blood products, they lack any characteristic appearance on CT or MRI
that allows discrimination from a neoplasm that has bled. Surgical resection
should be reserved for ovarian lesions that persist or grow on follow-up
imaging and that show no features on sonography indicating that they could be
definitively characterized as benign on MRI. Radiography has no role in the
evaluation of an adnexal lesion.
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