Pineal parenchymal tumors

Overview
Pineal parenchymal tumors arise from pineocytes or their precursors, and they are distinct from other pineal gland neoplasms such as astrocytic and germ cell tumors.

Pineocytoma (WHO grade II) is a slow-growing pineal parenchymal neoplasm that primarily occurs in young adults. Pineocytomas account for fewer than 1% of all brain tumors and comprise approximately 45% of all pineal parenchymal tumors. Adults aged 25 to 35 years are most frequently affected. No specific cytogenetic abnormalities or molecular genetics exist with this tumor. The 5-year survival rate has been reported to be as high as 86%.

Pineoblastoma (WHO grade IV) is a highly malignant primitive embryonal tumor of the pineal gland that manifests primarily in children. Pineoblastomas are rare brain tumors that comprise approximately 45% of all pineal parenchymal tumors. No specific cytogenetic abnormalities or molecular genetics exist with this tumor. Tumors similar to pineoblastomas in appearance have been observed in patients with familial (bilateral) retinoblastoma. Projected 1-, 3-, and 5-year survival rates of pineoblastoma patients treated by various modalities are 88%, 78%, and 58%, respectively.

Pineal parenchymal tumors of intermediate differentiation are monomorphous tumors exhibiting moderately high cellularity, mild nuclear atypia, occasional mitosis, and the absence of large pineocytomatous rosettes. They comprise approximately 10% of all pineal parenchymal tumors and occur in all age groups. No specific cytogenetic abnormalities or molecular genetics exist with this tumor. Clinical behavior is variable.