Immature teratoma of the tectum mesencephali with histopathological detection of rudimentary eye anlage in a 3-year-old boy: Report of a rare case

Intracranial teratoma is a rare neoplasm derived from omnipotent germinal cells that can contain mesoderm, endoderm and/or ectoderm layer tissue. Histologically teratomas are characterized by abnormal structures like teeth or bone that can be further subdivided into mature and immature according to the presence of incompletely differentiated tissue. Characteristic intracranial teratomas are space-occupying lesions in the pineal region and often present with hydrocephalic symptoms due to aqueduct stenosis. A 3-year-old boy presented with a peracute hemiparesis, fatigue and speech deficit. MRI diagnostics showed a cystic, partially solid, inhomogeneous contrast-enhancing formation at the top of the tectum mesencephali with consecutive aqueduct compression. The patient underwent a sub-occipital craniotomy via a supracerebellar approach and complete resection was achieved. The histopathological examination mainly showed mature tissue of ectodermal, mesodermal and endodermal origin. However, small areas of undifferentiated neuroectodermal tissue within an optic vesicle formation were detected, leading to the diagnosis of an immature teratoma. In due course, the patient was discharged in good health without neurological deficits. To our knowledge, optic vesicle-containing intracranial germ cell tumors are extremely rare. Here we report a unique case with immature neuroectodermal tissue within an optic vesicle formation in an otherwise mature teratoma.