International Journal of Gynecological Pathology 30:544–548, Lippincott Williams & Wilkins, Baltimore r 2011 International Society of Gynecological Pathologists Case Report Origin of Uterine Teratoma Differs From That of Ovarian Teratoma: A Case of Uterine Mature Cystic Teratoma Wen-Chung Wang, M.D., M.S., Mour-Shyuarn Lee, M.D., Jiunn-Liang Ko, Ph.D., and Yen-Chein Lai, Ph.D. Summary: Mature cystic teratomas are usually found in the ovaries and rarely in the uterus. Most teratomas of the uterus are of cervical origin. There are only a handful of reports to date of uterine teratomas arising from uterine corpus. The teratomas of the ovaries and the cervix are thought to be of parthenogenetic origin from oocyte after the completion of the first division. However, the origin of a uterine teratoma has not been established by molecular methods. In this study, we report a 46-year-old woman with a teratoma within uterine corpus. Computed tomography scanning and histological studies after tumor resection confirmed the diagnosis of teratoma. The DNA profiles of normal uterine tissue and teratoma tissue were compared using short tandem repeats analysis and showed that the teratoma did not originate from the parthenogenetic process. Our results suggest that the origin of this uterine teratoma is most likely pluripotential stem cell of uterus or primordial germ cell before meiosis I. Key Words: Uterine teratoma—Ovarian teratoma—Mature cystic teratoma—DNA profile—Short tandem repeat—Pluripotential stem cells. In ovaries, most benign teratomas are cystic, and thus are often referred to in clinical parlance as dermoid cysts (1). Cystic teratomas, which can contain several different tissue types, including skin, hair, muscle, and bone, are usually found in young women during their active reproductive years (1). They may be discovered incidentally, but are occasionally associated with clinically important paraneoplastic syndromes, such as inflammatory limbic encephalitits, which may remit on removal of the tumor (1). Benign teratomas are bilateral in 10% to 15% of cases (1). Other sites include midline structure of germ line cell migration. Benign cystic teratomas of the uterus are rare and are mostly present as cervical masses or polyps (2). In fact, there have been reports of only about 20 uterine cases over the last 80 years since the first report by Mann (3,4). No recurrence has been found either for tumor resection or hysterectomy, although malignant trans- formation of benign teratoma occurred in 1 case (2). In this study, we report a 46-year-old woman with a mature cystic teratoma within the uterine corpus. We compared the DNA profiles of normal uterine tissue and teratoma tissue using short tandem repeats (STR) analysis and clarified the origin of this tumor. CASE REPORT The patient was a 46-year-old Taiwanese woman (gravida 2 para 2). Her past obstetric history included 1 spontaneous vaginal delivery and 1 cesarean delivery. She reported regular menstrual intervals. Owing to palpable abdominal mass, she sought 544 DOI: 10.1097/PGP.0b013e31821c3205 From the Department of Obstetrics and Gynecology (W-C.W., M-S.L.), Jen-Ai Hospital; Chien-Tien Obstetrics and Gynecology Clinic (M-S.L.); Institute of Medical and Molecular Toxicology (J-L.K.); and School of Medical Laboratory and Biotechnology (Y-C.L.), Chung Shan Medical University, Taichung, Taiwan. The authors declare no conflict of interest. Address correspondence and reprint requests to Yen-Chein Lai, PhD, No.110, Sec. 1, Chien Kuo N. Road, Taichung (402), Taiwan, R.O.C. E-mail: yenchein@csmu.edu.tw.