Pineoblastoma UMLS:C0205898 SNOMEDCT_US:31671006 HP:0040193 Pineoblastomas are rare, malignant, pineal region lesions that account for <0.1% of all intracranial tumors. Pineoblastomas harbor a poor prognosis and can metastasize along the neuroaxis. Although they typically appear radiographically as a focal enhancing mass, pineoblastomas can be locally invasive and spread outside the pineal region through the subarachnoid space. Pineoblastomas are more common in children than in adults, and adults account for <10% of patients. Pinealoblastoma Pineoblastoma is a rare primitive neuroectodermal tumor (PNET) arising in the pineal gland. Pineoblastomas are classified as a WHO grade IV tumor and comprise one-fourth to one-half of pineal parenchymal tumors. Pineoblastoma is a highly cellular tumor originating in the pineal gland and containing small, poorly differentiated cells. Pineal parenchymal cell neoplasm