Pineal parenchymal tumours of intermediate differentiation - An evidence-based review of a new pathological entity

Pineal region lesions are uncommon, and pineal parenchymal tumours (PPT) account for 20-30% of tumours in this area of which pineocytomas (PCs) and pineoblastomas (PBs) are more prevalent. In 2007, the World Health Organisation (WHO) reclassified PPT from two subgroups (PC and PB) into four, including pineal parenchymal tumours of intermediate differentiation (PPTID). PPTID have been further divided into low- and high-grade lesions (WHO II and III), but due to their rarity have proven difficult lesions to diagnose and a paucity of literature means their optimal treatment options are a challenge to define. This article is a review of the literature of PPTID highlighting diagnostic criteria, a discussion on the role of surgery and radiotherapy, including treatment paradigms and reported outcomes for these problematic neoplasms.