A challenging imaging feature of mature teratoma in uterus

Mature cystic teratoma is a common benign germ cell tumor that typically develops in the gonads, whereas extragonadal teratomas are extremely rare, accounting for only 1%-2% of all germ cell tumors, with the uterus being an unusual site. We report a case of a 38-year-old woman who presented with prolonged abnormal vaginal bleeding following an abortion. Ultrasound and magnetic resonance imaging revealed a well-defined lesion located in the proximal endometrial cavity, showing internal vascularity and contrast enhancement similar to the surrounding myometrium, without diffusion restriction, macroscopic fat and fat suppression, or calcification on magnetic resonance imaging. Owing to the absence of the characteristic fat or calcified components typically reported in uterine teratomas, the lesion was preoperatively misdiagnosed as a submucosal myoma, and hysteroscopic resection was performed. Histopathological examination confirmed the diagnosis of a mature uterine teratoma. This case highlights a rare uterine teratoma with atypical imaging features, emphasizing that the lack of fat or calcification on magnetic resonance imaging can lead to diagnostic pitfalls and that uterine teratoma should remain in the differential diagnosis of submucosal-appearing uterine masses despite non-classic radiologic findings.