Case Report The Case of an Elderly Male Patient with Unknown Primary Mucinous Adenocarcinoma within Presacral Teratoma (Teratoma with Malignant Transformation) Ozgur Tanriverdi, 1 Ayca Ersen, 2 Suna Cokmert, 3 Emine Koca, 4 Naki Bulut, 5 Suha Gul, 6 and Nevin Yilmaz 7 1 Department of Medical Oncology, Sitki Kocman University Faculty of Medicine, 48000 Mugla, Turkey 2 Department of Pathology, Dokuz Eylul University Faculty of Medicine, 35010 Izmir, Turkey 3 Department of Medical Oncology, Kent Hospital, 35010 Izmir, Turkey 4 Department of Internal Medicine, Sitki Kocman University Faculty of Medicine, 48000 Mugla, Turkey 5 Department of General Surgery, Sitki Kocman University Education and Research Hospital, 48000 Mugla, Turkey 6 Department of Radiodiagnostics, Sitki Kocman University Education and Research Hospital, 48000 Mugla, Turkey 7 Department of Internal Medicine and Gastroenterohepatology, Sitki Kocman University Faculty of Medicine, 48000 Mugla, Turkey Correspondence should be addressed to Ozgur Tanriverdi; mugla.medicaloncology@gmail.com Received 14 September 2014; Revised 2 March 2015; Accepted 2 March 2015 Academic Editor: Cesar V. Reyes Copyright © 2015 Ozgur Tanriverdi et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Teratomas are rarely seen in adults, and presacral region is an area where they rarely settle in. Similarly, only about 1% of teratomas show malignant transformation. Malignant transformation is oten associated with the area where teratoma settles in. Malignant transformation of mediastinal teratomas is more frequent than the ones located in retroperitoneal area and gonad. hey most commonly show rhabdomyosarcoma, primitive neuroectodermal tumor, enteric adenocarcinoma, and leukemia transformation. In teratomas showing malignant transformation, the clinical course is aggressive; and survival of patients with metastatic disease is very low. he primary treatment of teratomas with malignant transformations is surgical. Efect of radiotherapy and chemotherapy is not clear in patients, to whom surgical operation cannot be applied, or those who are with residual tumor, even if surgical operation can be applied to them, or those who are at metastatic stage. In this paper, we presented a 76-year-old male patient due to the histologic diagnosis of mucinous adenocarcinoma within teratoma, in whom approximately 7 cm presacral mass was found during the radiographic examination made by the reason of low back pain and pelvic pain. 1. Introduction Tumors settled in presacral region are highly rare [1–3]. Such tumors may have developed congenitally or by acquisition. Additionally, the frequency of tumors settled in presacral area was reported to be 1/10000. Only 10% of such tumors are seen in adults, which develop usually in newborns or infants. In addition, 80% of adults with presacral tumor are women. hese tumors are usually benign, and only 1-2% of them shows malignant character [1–4]. Teratomas are the tumors most commonly seen in pre- sacral area in infants and newborns. he rate of teratoma incidence in infants and newborns was 1/35,000–40,000, with the dominance of male gender, while the ratio was determined to be 1/40,000–63,000 in adults, with a higher incidence in women [1–3]. In adults, malignant transforma- tion rate of primary teratomas settled in presacral region was about 1%. Adult teratomas may be transformed into squamous cell carcinoma, adenocarcinoma, sarcoma, and other malignancies [4–9]. While there were numerous reports on malignant trans- forming, including mucinous, adenocarcinoma, or squa- mous, from teratomas of ovary and testicle, no case of unknown primary mucinous adenocarcinoma within pre- sacral teratoma in an adult male was found in English literature. In this paper, we presented the case of mucinous Hindawi Publishing Corporation Case Reports in Oncological Medicine Volume 2015, Article ID 170479, 5 pages http://dx.doi.org/10.1155/2015/170479