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Sagittal MRI showing pineoblastoma
|Cell of origin||neuronal precursor|
Pineoblastoma is highly malignant, primitive embryonal tumor of the pineal gland. These lesions correspond to WHO Grade IV.
Pineoblastoma accounts for about 4% of all pineal parenchymal tumors. These lesions usually arise in the first two decades of life. There is a slight male predominance.
Pineoblastomas arise from the parenchyma of the pineal gland.
Signs and symptoms are related to mass effect in the region of the pineal gland, e.g. hydrocephalus, neuro-ophthalmologic dysfunction, changes in mental status, brainstem dysfunction, hypothalamic dysfunction, or cerebellar findings.
MRI demonstrates a heterogeneously enhancing, large and often lobulated mass lesion in the region of the pineal gland.
Pineoblastomas are soft and friable tumors. Infiltration of the surrounding structures is frequent, and these lesions are poorly demarcated from the surrounding brain. Calcifications are rare. Necrosis and intra-tumoral hemorrhage may be present.
Pineoblastomas are composed of patternless sheets of densely packed small blue cells with round-to-irregular nuclei and scant cytoplasm. Homer-Wright and Flexner-Wintersteiner rosettes may be seen. The high cellularity, presence of multiple mitoses, and lack of pineocytomatous rosettes differentiate pineoblastoma from pineocytoma.
Pineoblastoma may occur in patients with bilateral retinoblastoma (“trilateral retinoblastoma syndrome.”). The genetic basis of sporadic pineoblastoma has not been elucidated.
Seeding of the CSF is common, and extracranial metastasis may occur. Projected 1-, 3- and 5-year survival of patients with pineoblastoma who have received aggressive multi-modality therapy are 88%, 78% and 58%, respectively. Mean survival time following surgical intervention is 25.7 months.