Rom J Morphol Embryol 2016, 57(4):1389–1395 ISSN (print) 1220–0522 ISSN (online) 2066–8279 CASE REPORT Intracranial immature teratoma with a primitive neuroectodermal malignant transformation – case report and review of the literature CARMEN GEORGIU 1,2) , IULIAN OPINCARIU 3,4) , CRISTINA-LIGIA CEBOTARU 5) , ŞTEFAN-CLAUDIU MIRESCU 2,6) , BOGDAN-PETRE STĂNOIU 7) , TEODORA ANA MARIA DOMŞA 1,2) , ALINA SIMONA ŞOVREA 8) 1) Discipline of Pathology, Department of Morphological Sciences, “Iuliu Haţieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania 2) Department of Pathology, Emergency County Hospital, Cluj-Napoca, Romania 3) Discipline of Anatomy and Embryology, Department of Morphological Sciences, “Iuliu Haţieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania 4) Department of Radiology, Emergency County Hospital, Cluj-Napoca, Romania 5) “Prof. Dr. Ion Chiricuţă” Oncological Institute, Cluj-Napoca, Romania 6) Department of Molecular Biology and Biotechnology, “Babeş–Bolyai” University, Cluj-Napoca, Romania 7) Discipline of Cell and Molecular Biology, University of Medicine and Pharmacy of Craiova, Romania 8) Discipline of Histology, Department of Morphological Sciences, “Iuliu Haţieganu” University of Medicine and Pharmacy, Cluj-Napoca, Romania Abstract Introduction: Central nervous system (CNS) germ cell tumors are very rare, accounting for 0.3–3% of primary intracranial neoplasms; of these, the teratomas are even more uncommon. The immature variant of teratomas, defined by the presence of incompletely differentiated components resembling fetal tissues is considered as having a low, almost borderline malignancy state. Case presentation: A 35-year-old male presented with a left fronto-basal tumor. At surgery, a grey white tumor, mostly solid, was excised. The histopathological examination revealed an infiltrating teratoma. The histological spectrum varied from epithelial and mesenchymal mature to immature tissues. These structures were intimately mixed with significant areas of primitive neuroepithelial tubules and/or primitive neuroectodermal tissues. The diagnosis was that of an immature intracranial teratoma, with high histological grade WHO (World Health Organization) (Norris grade III). After surgical resection, a rapid infratentorial contralateral subarachnoid extension followed. The second tumor was largely formed by primitive neuroectodermal tumor (PNET)-like structures and rare mature epithelial tissues, meaning a PNET-like overgrowth or “malignant transformation” of an immature teratoma. After specific oncological treatment, the patient had a favorable evolution with no signs of relapse (2016). Conclusions: The present case highlights the value of the Norris grading system (mostly used in grading ovarian immature teratomas) in a very rare case of intracerebral immature teratoma with rapid subarachnoid extension caused by an unexpected secondary “malignant transformation”. Keywords: teratoma, immature, neuroectodermal, intracranial, overgrowth.  Introduction Central nervous system (CNS) germ cell tumors are very rare, accounting for 0.3–0.6% of all primary intra- cranial tumors in the West, to 2–3% in far-east Asia, were the incidence of CNS germ cell tumors appears to parallel the greater frequency of their testicular counterparts [1, 2]. These tumors preferentially affect the midline structures of the brain, around the third ventricle, especially the pineal gland and the suprasellar compartment, and rarely other sites. Only 6.2% of patients are older than 35 years, and just in exceptional cases have late adult onset [1]. A clear excess of cases involves males (73%), especially teratomas (89%) [1]. Intracranial pure teratomas are uncommon, the histologically immature variant and those with secondary “malignant transformation” being exceedingly rare [1]. Mature intracranial teratomas consist exclusively of mature, fully differentiated tissues and are potentially curable by gross total resection [1]. Immature intracranial teratomas consist of immature, embryonic or fetal tissues, exclusively, to small amounts, admixed with mature tissues. Hypercellular embryonic mesenchyme, primitive neuro- ectodermal elements, clefts lined by melanotic neuro- epithelium are more frequently encountered, and represent histological clues for the diagnosis of immaturity [1–3]. The immature variant of teratomas appears to occupy an intermediate position in terms of biological potential (survival rates after combined chemotherapy and irradi- ation, local recurrence, cerebrospinal fluid dissemination or hematogenous spread) [1, 2], between mature teratomas and high risk germ cell tumors of the brain (yolk sac tumors, embryonal carcinomas, choriocarcinomas and mixed lesions). Intracranial teratomas with malignant transformation or with a secondary malignant compo- nent contain an additional malignant component of con- ventional somatic type [1, 2, 4], composed of a single type of atypical cell population, with nodular or infiltrative pattern, mostly of carcinoma, sarcoma, primitive neuro- R J M E Romanian Journal of Morphology & Embryology http://www.rjme.ro/