Defined as an ectopic ovarian tissue without any connection with the utero-ovarian ligament, broad ligament, or infundibulopelvic ligament, a supernu- merary ovary is an extremely rare gynecological anomaly. It was first described by Winckel in 1890. The supernumerary ovary is unrelated to normal ovaries but has a normal ovarian function, although they may also sometimes be non-functional. 1-3 In this paper, we report the clinical, radiological, and histopathological features of a supernumerary ovary in the right abdominal region that was excised la- paroscopically, and diagnosed histopathologically. CASE REPORT A female infant born at 39 th gestational week had been found to have an abdominal cystic mass by pre- natal ultrasonography (US) at 28 th week of gestation. US was performed right after birth (Figure 1A), and a magnetic resonance imaging (MRI) examination had revealed that the abdominal cystic mass con- tained patchy semisolid components within a hemor- rhagic or mucinous fluid (Figure 1B, Figure 1C). Surgery had been recommended for the lesion, but the patient’s parents had refused it. The patient was referred to our hospital for jaundice 3 months later. In laboratory studies, she had a hemoglobin level of 7.7 g/L, a thrombocyte count of 17,000/mm 3 , and an indirect bilirubin level of 4.6 mg/dL. On ex- amination, there was a mass with a size of approxi- mately 5 cm on the right side of the abdomen. US examination showed no significant morphological change but a modest increase in size compared to the Turkiye Klinikleri J Case Rep. 2022;30(2):149-52 149 Supernumerary Ovary Characterized by Cystic Changes in the Omentum: A Rare Pathology Levent CANKORKMAZ a , Mehmet Haydar ATALAR b , Hatice ÖZER c , Gökhan KÖYLÜOĞLU d , Nisa BAŞPINAR b a Department of Pediatric Surgery, Sivas Cumhuriyet University Faculty of Medicine, Sivas, Türkiye b Department of Radiology, Sivas Cumhuriyet University Faculty of Medicine, Sivas, Türkiye c Department of Pathology, Sivas Cumhuriyet University Faculty of Medicine, Sivas, Türkiye d Department of Pediatric Surgery, İzmir Kâtip Çelebi University Faculty of Medicine, İzmir, Türkiye This study was presented as a poster in “55. Türkiye Milli Pediatri Kongresi”, October 12-16, 2011, Antalya, Türkiye. ABSTRACT Supernumerary ovary is a rarest gynecologic condition in children. The presence of cystic changes within the supernumerary ovary is extremely rare. We report a case of neonate with supernumerary ovary. The patient was 3-month-old girl with a right-side cyst diagnosed by a prenatal ultrasonographic evaluation. Ultrasonography performed right after birth, and a magnetic resonance imaging examination had revealed that the abdominal cystic mass contained patchy semisolid components within a hemorrhagic or mucinous fluid. Laparotomy revealed a cystic mass which has no connection with the normal reproductive organs. Two normal ovaries were identified in the abdominal cavity. After excision, histopathologic study revealed that cystic mass was supernumerary ovary on the omentum. The baby had no postoperative complications. Pre- natal differential diagnosis of abdominal cystic masses in infants with supernumerary ovary will be useful to keep in mind. Keywords: Supernumerary ovary; neonatal ovarian DOI: 10.5336/caserep.2021-87516 CASE REPORT Correspondence: Levent CANKORKMAZ Department of Pediatric Surgery, Sivas Cumhuriyet University Faculty of Medicine, Sivas, Türkiye E-mail: lcankorkmaz@gmail.com Peer review under responsibility of Turkiye Klinikleri Journal of Case Reports. Received: 14 Dec 2021 Received in revised form: 16 Feb 2022 Accepted: 17 Feb 2022 Available online: 25 Feb 2022 2147-9291 / Copyright © 2022 by Türkiye Klinikleri. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Turkiye Klinikleri Journal of Internal Medicine Türkiye Klinikleri Journal of Case Reports