Pineal parenchymal tumors

Pineal parenchymal tumors comprise a group of related tumors ranging from relatively benign to highly malignant. There are 5 diagnoses currently recognized in the 5th edition (2021) WHO classification of CNS tumors ⁴:

• pineocytoma
  • 14-30% of pineal parenchymal tumors ²
  • mature well-differentiated tumor
  • WHO grade 1
• pineal parenchymal tumor of indeterminate differentiation
  • 20-62% of pineal parenchymal tumors ²
  • WHO grade 2 or 3
• papillary tumor of the pineal region
  • yet to be graded but probably equivalent to WHO grade 2 or 3 ²
• pineoblastoma
  • 24-50% of pineal parenchymal tumors ²
  • malignant, primitive tumors
  • WHO grade 4
• desmoplastic myxoid tumor of the pineal region, SMARCB1-mutant
  • rare
  • only added to 5th edition WHO classification (2021)

As you can tell from the proportions given above, there is wide variation in the reported figures from series to series, which probably reflects the overall rarity of these tumors (and thus small series) and variability in the grading and terminology used.

Terminology

The term pinealoma was historically used to refer to both pineal parenchymal tumors and germinomas ³. This term has since fallen in popularity in the last several decades.