Intracranial immature teratoma with a primitive neuroectodermal malignant transformation - case report and review of the literature.

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".