Diagnostic Ultrasound - Abdomen and Pelvis

Ovarian Teratoma
TERMINOLOGY
Synonyms
• Dermoid cyst
Definitions
• Ovarian teratoma includes
○ Mature cystic teratoma (MCT) = dermoid cyst
○ Immature teratoma (IT)
○ Monodermal teratoma in which 1 cell line predominates
– Struma ovarii
– Carcinoid tumor
IMAGING
General Features
• Best diagnostic clue
○ Ovarian mass with echogenic shadowing mural nodule
(Rokitansky nodule) on US
Ultrasonographic Findings
• Grayscale ultrasound
○ Mature cystic teratomas have a variety of
appearances
– Heterogeneous cystic mass with echogenic
component
– Highly echogenic components due to fat content
– ± fat-fluid level
– Shadowing echogenic mural nodule (sebaceous
material)
□ Rokitansky nodule (a.k.a. dermoid plug)
– Hair
□ Punctate echoes in 1 plane
□ Elongate to become linear echoes in orthogonal
plane
□ Hair will move through more fluid component with
transducer pressure
□ Creates "dot-dash-dot" appearance
– Teeth
□ Highly echogenic focus/foci with distal acoustic
shadowing
– "Tip of the iceberg" sign: Only leading edge of mass
identified
□ Distal acoustic shadowing prevents assessment of
deep edge
□ Size cannot be measured
□ Mass may be much larger than suggested by
leading edge echoes
○ Immature teratoma: Heterogeneous, mainly solid,
scattered calcification (i.e., nonspecific)
○ Monodermal teratoma: Nonspecific sonographic
appearances
• Color Doppler
○ Look for flow in solid components
– Typically avascular
○ Beware of "twinkling" artifact, as sound reverberates on
calcified components
– Always perform pulsed Doppler evaluation of
apparent flow seen with color Doppler
Radiographic Findings
• May see associated calcification (e.g., "tooth" in pelvis)
CT Findings
• Fat-containing adnexal mass is diagnostic on CT
• 56% of MCT cases diagnosed on CT show
teeth/calcification
• IT: Characteristic appearance is mass with large irregular
solid component containing foci of fat and coarse
calcifications
○ Hemorrhage often present
• If ruptured, characteristic low density fat-containing
intraperitoneal fluid present
○ May lead to chemical peritonitis with mesenteric
stranding, peritoneal surface thickening
MR Findings
• T1WI
○ High signal components = fat
• T1WI FS
○ With fat saturation, loss of high T1 signal differentiates
fat from blood products
– ↓ signal = fat within teratoma
• T2WI
○ Variable intensity of fatty component, can be confused
with blood products
• IT: Characteristic appearance is mass with large irregular
solid component containing foci of fat and coarse
calcifications
○ Hemorrhage often present
Imaging Recommendations
• Best imaging tool
○ Ultrasound
– No ionizing radiation
DIFFERENTIAL DIAGNOSIS
Hemorrhagic Cyst
• Fine network of fibrin strands rather than floating hair
• Distal acoustic enhancement
○ Fat content in MCT causes sound attenuation (i.e.,
acoustic shadowing)
Endometrioma
• Homogeneous low-level internal echoes
• Often history of chronic cyclical pelvic pain, endometriosis
• No Rokitansky nodule
Torsion
• Complex enlarged adnexal mass
• Characteristically avascular but may occasionally see arterial
flow
• Any adnexal mass can act as lead point for torsion
Abscess
• Appendix abscess with appendicolith may mimic
sonographic appearance of ovarian teratoma
• Clinical presentation with pain/fever should suggest
diagnosis
• Infarcted dermoid may become infected
Bowel
• Use of TV sonography may help differentiate bowel from
normal ovary
Diagnoses: Female Pelvis
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