Case 8 - Answer

Nice job everyone. 

Answer: ovarian dermoid (aka teratoma)

US: usually the study of choice. Notice the complex mass with echogenic components. Associated “dirty” shadowing. No real Rokitansky nodule (dermoid plug) but there is the dot-dash pattern (ie think echogenic bands in dot-dash configuration) signifying thin complex echogenic material such as hair.  

CT:  an ovarian mass with large fatty component and a dermoid plug (Rokitansky nodule) - fairly classic appearing

references: https://radiopaedia.org/articles/mature-cystic-ovarian-teratoma

http://learningradiology.com/archives2007/COW%20273-Dermoid/dermoidcorrect.html