Pedunculated Adenomyoma with Osseous Metaplasia: A Case Report

We report a case of a pedunculated adenomyoma with osseous metaplasia, which mimics a dermoid cyst on magnetic resonance imaging (MRI) making it a considerable differential diagnosis. A 40-year-old female presented with chronic lower abdomen pain for a year. Pelvic MRI revealed a right-sided pelvic mass measuring 8.4 cm × 5.7 cm. The mass appeared isointense, with hyperintense contents similar to calcifications and fatty content. These results strongly indicated a dermoid cyst. During laparoscopy, a massive pedunculated uterine myoma was seen on the right posterior-fundal part of the uterus. During laparoscopic myomectomy, calcified tissues were discovered during manual morcellation. The histopathological examination confirmed the diagnosis of adenomyoma with widespread calcification and localized osseous metaplasia. Osseous metaplasia is an uncommon cytomorphological transformation seen mostly in the endometrium. Adenomyomas are rare, benign uterine tumors that are frequently misdiagnosed. In this case, the preoperative diagnosis suggested a dermoid cyst, broadening the differential diagnosis for calcified uterine tumors detected on MRI.