Mature cystic ovarian teratoma without intracystic fat: Case report with the "fat within the wall" sign.

Mature cystic teratoma is the most common ovarian neoplasm among young females. Diagnosed through radiological imaging as it exhibits typical radiological features; typically, fat. However, complete cystic teratoma without visible fat is a very rare and challenging diagnosis. It is difficult to distinguish it from malignant neoplasm, due to the presence of enhancing components, for example, Rokitansky nodule and the presence of diffusion restriction from keratinized products. We present a case of an incidental mature cystic teratoma without visible intracystic fat, where the correct diagnosis based on imaging was failed. Mature cystic teratoma was then confirmed upon histologic examination.