Abstract
BACKGROUND: Uterine leiomyomas are common uterine tumors, and typical cases of leiomyoma are easily diagnosed by imaging study. However, uterine leiomyomas are often altered by degenerative changes, which can cause difficulty and confusion in their clinical diagnosis. We describe the 17th reported case of a uterine leiomyoma clinically diagnosed as an ovarian tumor; however, the present case shows the most detailed radiological evaluation, including contrast-enhanced magnetic resonance imaging. We first show that a uterine leiomyoma can histologically mimic an adenomatoid tumor. CASE PRESENTATION: A 47-year-old premenopausal, nulliparous Japanese woman with a history of type 2 diabetes mellitus, hypertension, and hyperlipidemia had lower abdominal pain. Ultrasonography confirmed a 6-cm mass in the right-sided space of the pelvic cavity. Magnetic resonance imaging evaluation showed that a multilocular mass was present near the uterus, and a mucinous ovarian tumor was considered. Emergency surgery due to acute abdomen was performed under the diagnosis of pedicle torsion of the ovarian tumor. During surgery, a pedunculated uterine mass without stalk torsion was seen. The mass grossly contained serous and hemorrhagic fluids in the cavities, and pathology examination confirmed that the mass was a leiomyoma with hydropic and cystic degeneration. Anastomosing thin cord-like arrangements of the leiomyoma cells mimicked the architecture of adenomatoid tumors. The tumor cells were positive for the microphthalmia transcription factor but negative for other melanoma markers. Three days postoperatively, she was discharged without sequelae. CONCLUSIONS: Marked intratumoral deposition of fluids may induce the multilocular morphology of a tumor, and the cellular arrangement of the tumor cells with hydropic degeneration mimicked an adenomatoid tumor in this case. Clinicians need to be aware that a subserosal leiomyoma with cystic and hydropic degeneration can mimic an ovarian tumor, and pathologists should be aware that such leiomyomas can mimic adenomatoid tumors. Additionally, perivascular epithelioid cell tumors should not be diagnosed only based on its immunoreactivity for the microphthalmia transcription factor.