Figure
4d. Mature cystic teratoma of the right ovary in a 19-year-old
pregnant woman. (d) Photograph of the
gross specimen shows yellowish, pasty sebaceous material (black arrowhead) and
hair (white arrowheads) within the cyst cavity, findings that account for the
fat echogenicity and signal intensity seen at US and MR imaging. Two molar teeth
are also evident (arrows).
Figure 4(a) Sagittal transabdominal US image shows an echogenic mass with sound attenuation (arrows).
Abstract
Ovarian teratomas
include mature cystic teratomas (dermoid cysts), immature teratomas, and
monodermal teratomas (eg, struma ovarii, carcinoid tumors, neural tumors). Most
mature cystic teratomas can be diagnosed at ultrasonography (US ) but may
have a variety of appearances, characterized by echogenic sebaceous material
and calcification.
At computed tomography (CT), fat attenuation within a cyst is diagnostic. At magnetic resonance (MR) imaging, the sebaceous component is specifically identified with fat-saturation techniques. TheUS appearances
of immature teratoma are nonspecific, although the tumors are typically
heterogeneous, partially solid lesions, usually with scattered calcifications.
At CT and MR imaging, immature teratomas characteristically have a large, irregular solid component containing coarse calcifications. Small foci of fat help identify these tumors. TheUS
features of struma ovarii are also nonspecific, but a heterogeneous,
predominantly solid mass may be seen. On T1- and T2-weighted images, the cystic
spaces demonstrate both high and low signal intensity. Familiarity with the US , CT, and MR
imaging features of ovarian teratomas can aid in differentiation and diagnosis.
At computed tomography (CT), fat attenuation within a cyst is diagnostic. At magnetic resonance (MR) imaging, the sebaceous component is specifically identified with fat-saturation techniques. The
At CT and MR imaging, immature teratomas characteristically have a large, irregular solid component containing coarse calcifications. Small foci of fat help identify these tumors. The
Most mature cystic teratomas can be diagnosed
at US. However, the US
diagnosis is complicated by the fact that these tumors may have a variety of
appearances. Three manifestations occur most commonly. The most common
manifestation is a cystic lesion with a densely echogenic tubercle (Rokitansky
nodule) projecting into the cyst lumen (16). The second manifestation is a diffusely or partially
echogenic mass with the echogenic area usually demonstrating sound attenuation
owing to sebaceous material and hair within the cyst cavity (Fig 4) (17),(18). The third manifestation consists of multiple thin,
echogenic bands caused by hair in the cyst cavity (Fig 3). Pure sebum within the cyst may be hypoechoic or
anechoic (19). Fluid-fluid levels result from sebum floating above
aqueous fluid, which appears more echogenic than the sebum layer (18). The dermoid plug is echogenic, with shadowing due to
adipose tissue or calcifications within the plug or to hair arising from it.
Diffuse echogenicity in these tumors is caused by hair mixed with the cyst
fluid (Fig 4).
In a prospective US study that made use of
these criteria, Mais et al (20) found a sensitivity of 58% and a specificity of 99% in the
diagnosis of mature cystic teratoma. Numerous pitfalls have been described in
the US
diagnosis of mature cystic teratoma (21). Blood clot within a hemorrhagic cyst can appear
echogenic, although a mature cystic teratoma usually demonstrates sound
attenuation rather than increased through-transmission. Hemorrhagic cysts or
blood clots typically demonstrate increased through-transmission. Echogenic
bowel can frequently be mistaken for diffusely echogenic mature cystic teratoma
and vice versa (21). Perforated appendix with appendicolith and fibrous
lesions such as cystadenofibromas have also been described as false-positive
findings (21),(22).
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