Pineal parenchymal tumor of intermediate differentiation: a systematic review and contemporary management of 389 cases reported during the last two decades.

Pineal parenchymal tumor of intermediate differentiation (PPTID) is a WHO grade II and III tumor arising from pineal parenchymal cells. PPTID is a rare tumor accounting for less than 1% of all primary central nervous system neoplasms. Therefore, reports describing the clinical characteristics and biological features of PPTID are lacking. Moreover, the therapeutic strategy remains controversial. The current study aimed to evaluate treatment results and problems of contemporary therapeutic modalities of PPTID based on its features compared with other pineal parenchymal tumors. A comprehensive systematic literature review of 69 articles was performed, including articles on PPTID (389 patients) and similar tumors. Patient demographics, disease presentation, imaging characteristics, biological features, and current therapeutic options and their results were reviewed. We found that histopathological findings based on current WHO classification are well associated with survival; however, identifying and treating aggressive PPTID cases with uncommon features could be problematic. A molecular and genetic approach may help improve diagnostic accuracy. Therapeutic strategy, especially for grade III and aforementioned uncommon and aggressive tumors, remains controversial. A combination therapy involving maximum tumor resection, chemotherapy, and radiotherapy could be the first line of treatment. However, although challenging, a large prospective study would be required to identify ways to improve the clinical results of PPTID treatment.