Table 2.

Differential diagnosis of struma ovarii

	US	CT	MR
Struma ovarii	Heterogeneous mass with solid and multiple cystic areas Doppler: abundant and low resistance flow located centrally within the solid component	Multiloculated cystic mass with variable density between locules Calcifications might be present	Multiloculated cystic mass with variable signal intensity between locules on T2WI (“stained glass appearance”) ○ Areas of very low signal intensity on T1WI and T2WI (colloid material) Solid component with avid enhancement on enhanced T1images Presence of fat is not characteristic, unless it occurs in association with mature cystic teratoma Ascites can be present
Mucinous tumors (mucinous cystadenoma or cystadenocarcinoma)	Complex cystic mass with multiple locules showing variable echogenicity	Multiloculated ovarian mass with variable density between locules Calcifications might be present	Usually a large multiloculated cystic mass with variable signal intensity within locules (“stained glass appearance”) ○ Thick mucin (high signal intensity on T1W1 and low signal intensity on T2WI) ○ watery mucin (high signal intensity on T1W1 and low signal intensity on T2WI) Mucinous cystadenoma: thin regular cystic wall and septa; solid vegetations are usually not present Mucinous cystadenocarcinoma: thick and irregular cystic wall and septa; vegetations/soft-tissue component are typically seen
Mature cystic teratomas	Three types of appearance: Cystic lesion with an avascular and echogenic component (Rokitansky nodule) Diffuse or partially echogenic mass with sound attenuation (hair or sebaceous material) Cystic mass with linear echogenic strands (hair) Doppler US: blood flow detected at the periphery of the lesion	Cystic lesion with concomitant presence of fat (+/− fat fluid level) Teeth or wall calcifications may be also present	Cystic mass with fat component ○ High-signal intensity on T1WI ○ Fat-fluid or fluid-fluid level within the cystic cavity ○ Chemical-shift artifact useful in teratomas without demonstrable fat Teeth or calcifications may also be identified ○ Low-signal intensity on T1WI e T2WI Soft-tissue nodule in the cystic wall (Rokitansky nodule/dermoid plug) ○ No contrast enhancement